Laboratorystudiesofnewphotochemicalprocessesof
NOxandHOxinthemiddleandupperatmosphere
中層･高層大気におけるNOxおよびHOxの
新しい光化学過程の実験的研究
TomokiNakayama
中山智喜
NagoyaUniversity
2006
41425597
報告番号
甲第6839
号
主論文
題
目
LaboratorystudiesofnewphotochemicalprocessesofNOxandHOxinthe
middleandupperatmosphere
(中層･高層大気におけるNOxおよびHOxの新しい光化学過程の実験的研究)
Contents
Abstract
ChapterlGeneralintroduction
1
l.1Importanceofozoneinthemiddleatmosphere
2
l.2
4
l.3
ChemistryofNOxinthemiddleatmosphere
l.2.1NOxcyclesfbrozoneloss
4
l.2.2
5
ProductionanddestructionprocessesofNOx
ChemistryofHOxinthemiddleatmosphere
l.3･1HOxcyclesforozoneloss
l.3.2
ProductionanddestructionprocessesofHOx
l.4
ChemistryofNOintheupperatmosphere
l.5
0(1s)airglowintheupperatmosphere
ReftrencesfbrChapterl
Chapter2
Experimenta1
2.10ve,ViewofthedetectiontechniquesofN(4s)andO(1s)atoms
2.1.1DetectionteclmiquesofN(4s)atoms
2.1.2
2.2
2.3
DetectionteclmiquesofO(1s)atoms
VUV-LIFspectroscopy
6
6
7
9
10
21
23
23
23
23
24
2.2.1DetectionteclmiquesofN(4s)atoms
24
2.2.2
PrincipleofVUVlaserlightgeneration
25
2.2.3
PrincipleoftheDopplerpronlemeasurement
26
Experimentalsetup
2.3.1Reactionchamberandflowsysteni
26
27
2.3.2
Photolysislasers
27
2.3.3
TunableVUVlaserfordetectionofN(4s)atoms
27
2.3.4
TunableVUVlaserfbrdetectionofO(1s)atoms
28
2.3.5
Detectionsystemanddataacquisition
29
RefbrellCeSfbrChapter2
37
Chapter3
N(4s)fbrmationintheUVphotolysisofN20and
itsimpIicationsfbrstratosphericozonechemistry
39
3.1Introduction
39
3.2
Experimenta1
40
3.3
Results
41
3.3.1
Chemicaltitrationmethod
41
3.3.2
Photolyticcalibrationmethod
43
Discussion
3.4
44
3.4.1DissociationprocessofN20toproduceN(4s)+NO
44
3.4.2
45
Atmosphericimplications
54
RefbrencesforChapter3
KineticsoftheatmosphericreactionsofN(4s)atoms
Chapter4
55
WithNOandNO2
4.1Introduction
55
4.2
Experimenta1
57
4.3
Resultsanddiscussion
58
4.3.1N(4s)productionfo1lowing193nmlaserirradiationofNO
58
4.3.2
N(4s)productionfo1lowing193nmlaserirradiationofNO2
60
43.3
ReactionkineticsofN(4s)+NOandN(4s)+NO2
61
70
ReferencesfbrChapter4
Chapter5
TranslationalrelaxationofsuprathermalN(4s)atoms
intheupperatmosphere
72
5.1Introduction
72
5.2
Experimenta1
73
5.3
Experimentalresults
73
5.4
Modelcalculationsforhardspherecollisionradii
75
80
ReferencesforChqpter5
11
PhotochemicalreactionprocessesofO()s)and
Chapter6
theirimplicationsfbrOHproductionandairglow
81
6.1Introduction
81
6.2
Experimenta1
83
6.3
Resultsanddiscussion
84
6.3.1QuantumyieldsforO(ls)fbrmation丘omO3Photolysis
84
around200nm
6.3.2
DopplerproBleofO(ls)producedfromthephotolysisofO3
85
at193nm
6.3.3
QuantumyieldsforO(一s)formationfromN20andH202
86
Photolysisat193nm
6.3.4
6.4
ReactionkineticsofO(ls)withatmosphericmolecules
90
Atmosphericimplications
6.4.10Hproductioninthestratosphereandmesosphere
6.4.2
Dayglowemissioninthemesosphereandlowerthermosphere
90
92
108
ReftrencesforChapter6
Chapter7
87
Summaryandfutureperspective
Acknowledgments
iii
112
Abstract
Photochemicalreactions
a
radicalplay
offree
determinlng
crucialrolein
chemicalcompositionoftheatmosphere.Oddnitrogenradicals(NOx=N+NO+
NO2)andoddhydrogenradicals(HOx=H+OH+HO2)areimportantinthemiddle
catalytic
andupperatmosphere･ForexamPle,the
cycleincludingNOxis
amqor
removalprocessofozoneinthelowerandmiddlestratosphere,andthecatalyticcycle
includingHOxbecomesdominantO3Sinkintheupperstratosphereandmesosphere･
Therefbre,itisimportantforareliableassessmentoftheozonetrendtounderstandthe
photochemicalprocessesofNOxandHOx･Inthisstudy,thelaboratorystudieson
severalnewimportantPrOCeSSeSOfNOxandHOxinthemiddleandupperatmosphere
havebeenperformeduslnglaserspectroscopicteclmiques･
A
new
teclmiquefor
high-SenSitive
detection
ofthe
electronic
ground
state
nitrogenatom,N(4s),andtheelectronica11yexcitedoxygenatom,0(ls),hasbeen
developedinthis
were
study.TheN(4s)atoms
detectedbyvacuum
ultraviolet
laser-inducedfluorescence(VUV-LIF)teclmiqueat120.07nmwhichisresonantwith
theelectronictransitionN3s4plr2←2p4s3/2･Thesubsequentnuorescencefromthe
excited
stateis
directly observed
by
a
solar-blind photomultiplier･Tunable
Sum
generatedbytwo-Photonresonancefour-WaVe
radiationaround120･07nmwas
O(1s)atoms
frequencymixinginHgvapor･The
VUV
weredetectedbyVUV-LIF
teclmiqueat121･76nmwhichisresonantWiththeelectronictransitionO(3sIpl←
2pIso).TunableVUV
resonancefour-WaVe
radiationaround121･76nmwasgeneratedbytwo-Photon
difftrence丘equency
mixlngln
agaS
mixture
ofKr/Ar･The
VUV-LIFtechniqueutilizedinthisstudyhasaminimumsensltlVltyOf2×109and3×
108atomscm,3fordetectionsofN(4s)andO(1s),reSPeCtively.
InChapter3,theformationofN(4s)fromtheUVphotolysisofNitrousoxide
P20)andimpactonNOxfbrmationinthestratospherehasbeendescribed･N20is
knowntobeaprecursorofNOxinthestratosphere･Mostofstratosphericremovalof
N20transportedthroughplanetary
boundarylayerand
the丘eetroposphereto
stratosphereisphotolysisbythesolarUVradiationaround200nm,Whileasmall
fractionofN20reactswithO(1D)atoms.StratosphericNOxproductionisthoughtto
beduetothereactionofN20withO(1D).IfthephotodissociationchallnelofN20to
1V
the
produceN(4s)+NOexistwithasigni丘cantyield,itcouldbeanewsourceofNQxin
thestratosphere･lnthepresentstudy,thequantumyieldforN(4s)fbrmation丘om
N20photolysishasbeendeterminedtobe(2･1±0･9)×10,3at193nm･Asensitivity
analysistoassesstheimpactoftheN(4s)andNOformation&omN20photolysison
stratosphericchemistryhasbeenperfbrmeduslngaOne-dimensionalphotochemical
m｡del.WhenconsideringtheN(4s)+NOchannelasanadditionalphotolyticsinkof
N20,the
steady
stateNOx
to∼3%around25kmin
up
concentrationincreases
comparisonwiththatignoringtheN(4s)+NOchannel･
InChapter4,thereactionkineticsofN(4s)atomswithNOxhavebeendescribed･
The
actas
reactiol-OfN(4s)withNOisthoughto
a
upper
sinkofNOxinthe
stratosphere,meSOSPhereandthermosphere･Theexperimentalteclmiqueoflasernush
photolysISandtheVUV-LIFdetectionwasappliedforthenrsttimetothekinetic
st｡dies｡fthereactionsinvoIvingN(4s).TheN(4s)atomswereproducedfo1lowing
193nmArFlaserirradiationofNOandNO2･ThephotoexcitationprocessesofNO
andNO2givingrisetotheN(4s)fbrmationhavebeendiscussedindetail･Basedon
themeasurementsofDopplerpronlesofN(4s)atomsandphotolysislaserpower
dependence
ofthe
N(4s)LIFintensity,the
One-Photon
predissociativelyfo1lowlng
NO
N(4s)formation丘om
absorption,While
thatfrom
occurs
NO2includes
two-Photonprocesses･TherateconstantsforthereactionsofN(4s)withNOandNO2
at295±2Khavebeendeterminedtobe(3.8±0.2)×10-11and(7･3±0･9)×10-12
cm3molecules-1s-1,reSPeCtively･Thoseresultsarecomparedwiththeliteraturedata･
InChapter5,thecollisionalrelaxationprocessesofsuprathermalN(4s)atoms,
which
are
relevant
to
the thermosphere,have
NOformationin
been
described･
Althoughithadbeenproposedthataslgni丘cantamountoflower-thermosphericNO
m｡1ec｡1es
camefr｡m
the
reaction
suprathermalN(4s)atoms
of
with
O2,nO
experimentalevidenceofthereactionwasavailable･ThereactionbarrieroftheN(4s)
reactionwithO2WaSrePOrtedtobe∼0･24eV･Inthisstudy,thecompetitiveprocesses
oftheinelasticcollisionstoproduceNOandtheelasticco11isionstothermalizethe
translationalenergyofN(4s)have･beeninvestigatedfbrthereactionofsuprathermal
N(4s)reactionwithO2atinitialcenter-OflmasscollisionenergyofaboutO･24-0･6eV･
ThesuprathermalN(4s)atomswhichhaveanaveragetranslationalenergyofO･92±
0.095eVinthelaboratoryflamewereproducedby193nmphotolysISOfNO2inbath
gasofO2･Dopplerpro丘1esoftheN(4s)atomswererecordedbyVUV-LIFdetection
V
ofN(4s),丘omwhichtheaveragekineticenergyoftheN(4s)atomswereobtainedasa
function
ofthermalization
time.No
clearevidence
oftheNOproductionhas
been
Observed,Whichwi11beexplainedbyarelativelylargevalueofthethermalizationcross
SeCtioncomparedwiththeinelasticcollisioncrosssection.Monte-Carlocalculations
employlnganelastichard-SPhereco11isionmodelhavebeenperformedtoestimatethe
hard-SPherecollisionradiiandthermalizationcrosssection･Thethennalizationcross
SeCtion,Whichreproducedtheexperimentalresults,Were(3･8±0･4),(2･8±0.4),(1.8±
0.2),and(2.3±0.2)inunitsoflO15cm2forN(4s)+N2,02,HeandAr,reSPeCtively.
Thethermalizationcrosssectionswi11makeitpossibletoperformmoreprecisemodel
CalculationsforNOfbrmationprocessesinthethermosphere.
InChapter6,thephotolyticformationofO(1s)丘omtheUVphotolysisofO3
around200nmanditssubsequentreactionswithsmallmoleculesrelevanttomiddle
andupperatmosphericchemistryhavebeenstudied,andimpactonHOxformationin
thestratosphereandmesospherethroughO(1s)+H20reactionhasbeendescribed.
The
quantum
yield
fbr
O(1s)fbrmation五･Om
O3Photolysis
at295Khas
been
determinedtobe(2.5±1.1)×10-3,(1.4±0.4)×10-4and(5±3)×10-5,at193,215and
220nm,reSPeCtively.TherateconstantSforthereactionsofO(ls)withO2,CO2,H20,
03andHClat295±2Khavebeendeterminedtobe(2.85±0.31)×10,13,(3.09±0.29)
×10.)3,(6.38±0.38)×10.10,(4.63±0.45)×10.10and(5.47±0.27)×10.10
cm3molecules-1s-1,reSPeCtively･Basedonthepresentlaboratorydataweobtained,
impactoftheO(1s)fbrmationfromO3PhotolysisontheOHradicalformationinthe
StratOSPhereandmesospherehasbeeninvestigated･Ithasbeenconcludedthat,the
reactionofH20withO(1s)produced丘omO3Photolysisaround200nmprovidesanew
source
ofOHin
the
stratosphere
and
mesosphere,Whichis
up
to∼2･5%ofthe
conventiona10HproductionbyO(lD)+H20reactionat30kmaltitudeinmid-1atitude.
ImplicationsofthepresentresultsfortheterrestrialairglowofO(ls)at557･7nmhave
alsobeendiscussed.Ithasbeensuggestedthattheimpactofthedirectformationof
O(ls)fromO3Photolysisonthevolumeemissionrateislesssigni丘cantthanthe
fbrmationthroughthepreviouslyproposedBarthmechanism.
TheresultsinthisthesisshowthatthephotolyticformationofN(4s)andNO
fromN20canactasanewsourceofstratosphericNOx,andthatthereactionofH20
withO(ls)whichisformed丘omO3PhotolysiscanaCtaSaneWSOurCeOfstratospheric
andmesosphericHOx.ThesenewNOxandHOxsourcesshouldbetakenintoaccount
Vl
fbrdetailunderstandingofthechemicalprocessesinthemiddleandupperatmosphere･
The
results
PreSent
also
StudylS
demonstrate
a
VUV-LIF
that the
technlque
both
POWerfu1tooltoinvestlgate
the
moleculesandthekineticsinvoIvingN(4s)andO(ls)atoms.
vii
which
developedin
photodissociation
the
ofsmall
Chapterl
GeneralIntroduction
TheEarth,satmosphereiscommonlydescribedasaseriesoflayersde血edby
their
thermalcharacteristic･Thelowestlayer,Called
the
troposphere,eXhibits
generallydecreaslngtemPeratureSwithincreaslngaltitudesuptoaminimumcalledthe
tropopause･Thetropopauselocatesnear12kmattheequatorandnear8kninpolar
the
reglOn･Above
temperatures
located
tropopause,the
withincreaslngaltitudesupto
amaximum
high
near50km･Atfurther
begins,eXhibitingincreaslng
stratosphere
atthelevelofstratopause
altitudes,the
begins,eXhibiting
mesosphere
decreaslngtemPeratureagalnuPtOaminimumatthelevelofmesopausenear85kn.
ThereglOnlocatedabovethemesopauseiscalledthermosphere･Thetemperatures
thereincreaseveryrapidlywithaltitude･Thealtituderangebetween12andlOOkm,
Whichalmostcorrespondstothestratosphereandthemesosphere,isgenerallycalled
′′middle atmosphere′′･The
altitude
abovelOO
km,Which
corresponds
to
the
thermosphere,1Sgenera11ycalled′′upperatmosphere′′･Mostofthechemistrylnthe
middleandupperatmospheresisdrivenbysolarlight･Thephotochemicalprocesses
OffreeradicalsplayacrucialroleindetermlnlngChemicalcompositionofthemiddle
andupperatmosphere.
Inthemiddleatmosphere,OZOne(03)isthemostimportantChemicalconstituent,
becauseitisthe
onlyatmospheric
speciewhichefficiently
absorbsultraviolet
solar
radiation･Theozoneconcentrationsinthemiddleatmospherearecontrolledmainly
by
catalytic
reactionsinvoIving
the
odd
nitrogens,NOx(=N+NO+NO2),Odd
hydrogens,HOx(=H+OH+HO2),andoddchlorines,ClOx(=Cl+ClO).The
CatalyticcycleincludingNOxisam毎orremovalprocessofozoneinthelowerand
middlestratosphere,andthecatalyticcycleincludingHOxbecomesdominantinthe
upper
stratosphereand
mesosphere[1]･Therefbre,detailedunderstanding
ofthe
PrOductionanddestructionprocessesofNOxandHOxinthemiddleatmosphereis
important.
In
the
upper
atmosphere,nitric
oxide
PO)is
one
ofthe
COnStituents･Emissionat5･3トLm丘omNOisanilnPOrtantCOOlingmechanisminthe
mostimportant
NO
thermosphere[2]･The
thermosphere
middle
molecules
canbetransportedintothemiddleatmosphere
atmospheric
high-1atitude,lower
the
producedin
whereitcouplesinto
chemistry･Theunderstandingoftheproductionandremoval
PrOCeSSeSOfNOinthethermosphereiscruCial･Ithasbeenrecognizedfbrmanyyears
thatobservations
ofthe
alrglowemissionrates
should
provide
apowerfu1toolfbr
remotelysenslngthestateoftheupperatmosphere･Themostfrequentlyobserved
the
emissionis
O(ls)greenline
atomic
emission
at557.7nm.This
emissi｡n
Particularlyprovidestheinformationaboutthevariabilityofsolaractivityandatomic
OXygen
the
COnCentrationin
upper
atmosphere･The
understanding
ofthe
O()s)
PrOductionprocessesisalsoimportant･
ThisthesisfocusesonthephotochemicalprocessesrelatedtoNOxandHOxin
themiddleandupperatmosphere･Thelaboratorystudiesonsomenewprocessesof
NOxandHOxinthemiddleandupperatmospherehavebeenperformeduslnglaser
SPeCtrOSCOPICteClmiques･Inthischapter,theimportanceofozoneandchemistryof
NOx
and
HOxrelated
to
ozoneinthe
middle
atmosphereis
described.Then,the
importanceofNOal-dO(ls)airglowemissionintheupperatmosphereisdescribedin
detail.
1･1Importanceofozoneinthemiddleatmosphere
Ozoneiscentralinhighlycoupledchemical,radiative,anddynamicalprocesses
OfEarth,smiddleatmosphere,aSShowninFigurel･1･OzoneisproducedbyO2
Photolysis
and
destroyed
by
photochemicalreactionsinvoIving
radicals
whose
COnCentrationdependsontheozoneabundanceasdescribedbelowindetail.Ozone
andotherconstituentsaretranSPOrtedbywindsthatarerelatedtothetemperature
distributionanddrivenbyabsorptionintheatmosphereofvertica11ypropagatingwaves.
Ozoneabsorbssolarultraviolet(UV)radiationbetween240and320nmwhichwould
Otherwise
tranSmitted
to
the
Earth,s
surface･Such
radiationislethalto
simple
unimolecuarorganismsandtothesurfacecellsofhigherplantsandanimals･Heating
Ofthemiddleatmospherefo1lowlngtheabsorptionbyozoneofsolarUV,Visibleand
Earth-emittedinfrared(IR)radiationcontributestocharacteristictemperaturepronleof
themiddleatmosphere･Stratosphericairisstaticallystablebecauseoftheincreasein
temperaturewithaltitude･Ozoneabsorptionalsoprovidesaslgni丘cantenergySOurCe
fordrivingthecirculationofthemesosphereandforclngtidesintheuppermesosphere
2
andthermosphere.
ThemixlngratioofozoneistypICallylOO-500ppbvattropopause,3ppmvat20
km,8-10ppmvat35km,and2ppmvatstratopause[1,3].AlthoughtheimportanCeOf
atmospheric
intensified
has
ozone
been
dramatically
COnCernthatavariety
thanSixty
more
recognizedfor
been
years･Interesthas
overthelastthirty
has
years,reSearCh
stimulatedby
detectablechangeSinthe
ofhumaninnuencesmightleadto
abundanCeOfozoneinthemiddleatmosphere･Itisnowapparentthatstratospheric
OZOne
have
COnCentrations
been
declining
over
decades
two
past
dramatic
and
depletionsofozoneovertheAntarcticeachyear.
In1930,Chapman[4]nrst
destruction
to
thatlead
reactions
proposed
a
state
steady
thefundamentalozone-formingand
concentration
the
ofO3in
middle
atmosphere･Thereactionskn0wnaStheChapmanmechanismare
02+hv→20
(1.1)
0十02+M→03+M
(1.2)
O3+hv→02+0
(1.3)
0+03→202.
(1.4)
Becausereactions(1.2)and(1.3)rapidlyinterconvertOandO3,itisusefu1tothinkof
thesumofOandO3aSaSinglespecies,Oddoxygen(Ox=0+03).Oddoxygenis
PrOducedonlyinreaction(1･1)andislostinreaction(1.4).Ozoneisthedominant
fbrmofoddoxygenbelow∼60km.
Untilabout1964,itwasthoughtthattheChapmanmechanism,OXygen-0nly
reactions,COuld
explain
ozone
atmospheric
However,improved
abundanCeS･
laboratorymeasurementsoftherateconstantofreaction(1.4)indicatethatthereaction
is considerably
slower
than
thought.Then
previously
the丘eld
measurements
indicatedthattheactualamountofozoneinthestratospllereWaSaboutafactorof21ess
thallthat what
destruction
was
predicted
pathway(S)are
bythe
needed
ChapmanmeChanism.Thus,additionalozone
beyond
reaction(1.4).Bates
Nicolet[5]
and
introducedtheideaofcatalyticoddoxygenlossprocessinvoIvinghydrogenradicals.
Crutzen[6]andJolmston[7]revealedtheroleofcatalyticoddoxygenlossprocess
invoIvingnitrogenoxides･StolarskiandCicerone[8],MorinaandRowland[9]and
RowlandandMorina[10]elucidatedtheef托ctofchlorine-COntainingcompoundson
OZO11eChemistry.
The
ozone
destruction
that
processes
3
must
be
added
to
the
Chapman
mechanismtakethefbrmofacatalytlCCyCleinvoIvingNOx,HOx,ClOx:
Ⅹ+03→Ⅹ0+02
Ⅹ0+0→Ⅹ+02
Net:03+0→02+02,
WhereXisfreeradicalcatalyst･XcanbeH,OH,NO,OrCl･Theabovecycleis
CatalytlCinthatXisnotconsumedintheprocess･Thenetresultofthecycleisthe
COnVerSionoftwooddoxygenspecies(03andO)totwoevenspecies(202).Odd
OXygenisneededtoproduceO3･Therelativeimportanceofthecyclecorresponding
toaparticularXspeciesdependsontheconcentrationofXandtherateconstantsofthe
reactionsinthecycle･Formostofsuchcycles,reaCtion(1.5)occursrapidlysothatthe
rate-determiningstepisreaction(1.6)[1].
Figure･1･2showstherelativecontributionoftheHOx,NOx,ClOxcyclesaswell
asoftheoxygen-OnlyChapmanreactionstooddoxygendestruction･Itisapparent
thatthecatalyticcyclesinvoIvingNOxmakeamqorcontributiontodestructionofodd
OXygeninthemiddlestratosphere,WhilethecatalyticcyclesinvoIvingHOxbecome
moreimportantintheupperstratosphereandmesosphere･ChemistryoftheNOxand
HOxinthemiddleatmosphereisdescribedindetailinthefo1lowingsections(Section
l.2andl.3).
1･2ChemistryofNOxinthemiddleatmosphere
l.2.1NOxcyclesIbrozoneloss
ThecatalyticcycleinvoIvingNOxmakesam毎orcontributiontodestructionof
Oddoxygeninthemiddlestratosphere(25-35km):
Cyclel
NO+03→NO2+02
NO2+0→NO+02
Net:03+0→202.
Inthelowerstratosphere,reaCtion(1.8)isreplacedbythephotodissociationofNO2:
NO2+hv→NO+02
(1.9)
Thereaction(1･9)nulli丘estheozoneremoval･Inthelowerstratospherewhereozone
ismoreprevalent,anOtherNOxcycleis
Cycle2
NO+03→NO2+02
NO2+03→NO3+02
NO3+llV→NO+02
4
Net:203→302.
during
MostatmosphericNO3formedbyreaction(1･10)isremovedbyphotolysis
daytime.TheproductsofphotodecompositionareNO2+0(inwhichcasethereisno
netlossofoddoxygen),andNO+02(inwhichcaseoddoxygenisconsumed)･The
nitrateradicalcanalsoreactwithNO2tOPrOducedinitrogenpentaoxide,N205:
(1.12)
NO3+NO2+M→N205+M
N205CandecomposebacktoNO3andNO2eitherphotolyticallyorthermally･Since
itsformationdoesnotrepresentapermanentlossofNOx･N205isareservoirspecies
払rNOx.
ThechemistrylnVOIvingNOxiscloselyintertwinedwiththatofClOxandHOx,
forexample,byfo1lowlngreaCtions:
NO+ClO→NO2+CI
(1.13)
NO+HO2→NO2+OH
(1.14)
NO2+ClO+M→C10NO2+M
(1.15)
NO2+HO2+M→HO2NO2+M
(1.16)
NO2+OH+M→HNO3+M.
(1.17)
BecauseClOandHO2aretheanalogsofNO2intheiroddoxygendestructioncycles,
theoccurrenceofreaction(1.13)or(1.14)enhancestheimportanceofNOxdestruCtion
cyclebutdiminishestheC10xandHOxcatalyticcycles･Nitricacid(HNO3),Chlorine
nitrate(ClONO2),andpemitricacid(HO2NO2)producedinthereactions(1･15-17),
saveastemporaryreservoirsforNOx,ClOxandHOxtakingthemoutoftheirozone
destruCtioncycles[3].
1.2.2ProductionanddestructionprocessesofNOx
TheprincipalnaturalsourceofNOxinthestratosphereisnitrousoxideP20)
producedattheearth,ssurfacebybiologlCalprocesses･MostoftheN20tranSPOrted
tothestratospherethroughtheplanetaryboundarylayerandthefreetroposphere･
Figurel.3ashowsanUVabsorptionspectrumofN20[11]･Figurel･4showssolar
photonfluxataltitudesof50,30,andOkm,reSPeCtively,aSafunctionofwavelengthat
solarzenithangle(SZA)of500.Thewavelengthregionbetween185and220nmisin
so-Called=stratosphericwindownwherenon-negligiblesolarPhotonscanpenetrateinto
thestratosphericaltitudesduetothegapofShumann-RungebandofO2andtheHartley
5
bandofO3aSShowninFigurel･4･Approximately90%ofN20inthestratosphereis
destroyedbyphotolysISarOund200nmasshowninFigurel.5,
N20+hv→N2+0(lD),
Where
thelong
(入<341nm)
(1.18a)
the
wavelengthlimitgiveninparenthesesindicates
thermochemical
thresholdforchannel(1･18a)･Theremainder,∼10%ofN20inthestratosphere,reaCtS
withO(lD):
N20+0(lD)→2NO
(1.19a)
(1.19b)
→N2+02･
Reaction(1.19a)isknowntobethemainsourceofNOxinthestratosphere.About
58%oftheN20+0(】D)reactionproceedsviacharmel(1.19a),theremaining42%by
Channel(1.19b)[11].
Although
(1.18a)with
has
N20photolysis
an
almost
been
quantum
unit
to
considered
proceed
through
channel
yield[12],Channels(1.18b-d)are
also
energeticallypossible.
(入<248nm)
(1.18b)
→N2+0(3p)
(入<742nm)
(1.18c)
→N2+0(ls)
(入<211nm).
(1.18d)
N20+hv→N(4s)+NO
Ifchannel(1.18b)occurredwithasignincantyield,itcouldbeadirectsourceofNOxin
thestratosphereasshowninFig.1.5.Inthisthesis,thephotolyticformationofN(4s)
from
the
UV
photolysis
ofN20through
on
channel(1.18b)anditsimpact
NOx
formationinthestratospherehavebeendescribedinChapter3.
ThereactionofN(4s)withNOisconsideredasthedestructionprocessofNOx
intheupperstratosphereandmesosphere:
N(4s)+NO→N2+0.
(1.20)
TheN(4s)atomsaremainlyproducedbyphotodissociationofNOinthemiddle
atmosphere.Inthisthesis,thereactionkineticsoftheN(4s)withNOandNO2have
beendescribedinChapter4.
1.3ChemistryofHOxinthemiddleatmosphere
l.3.1Ⅲ0ⅩCyCleslbrozoneloss.
OH
Chemistry
Partitionlng
and
either
HO2Play
as
direct
Withil-Other
a
stratospheric
criticalrolein
reactants
with
odd
chemicalfamilies･The
6
oxygen
and
or
catalytic
mesospheric
through
controlof
cycleinvoIving
ozone
the
HOx
COntributes slgni丘cantlyto
destructionofoddoxygenintheupperstratosphere
and
mesosphere.
Aboveabout40km,them句OrCatalytlCCyClesinvoIvingOHare
Cycle3
OH+0→H+02
H+02+M→HO2+M
HO2+0→OH+02
Net:20→202,
and
Cycle4
OH+0→H+02
H+03一}OH+02
Net:0+03→202.
Between30and40km,Cycle5becomesimportant:
Cycle5
0H+03→HO2+02
HO2+0→OH+02
Net:03+0→202.
Below
there
about30km,Where
are
veryfew
oxygen
atoms,Cycle6becomes
dominant:
Cycle6
OH+03→HO2+02
HO2+03→OH+202
Net:203→202.
TherelativeimportanceofthecycleschangesastheconcentrationsofkeyreactantS(H,
OH,andHO2)andthetemperaturechange.InteractionofHOxwithNOxandC10xis
importantasdescribedintheprevioussectionfbrthecaseofNOx.Inadditiontothe
COuPlingbetweenHOxandNOxbyreactions(1.14),(1.16),and(1.17),thecoupling
betweenHOxandClOxoccurredbyreactions(1.27)and(1.28)[3]:
OH+HCl→H20+CI
HO2+ClO→HOCl+02.
1.3.2ProductionanddestructionprocessesofHOx
ThesourceofHOxinthemiddleatmosphereislargelywatervapor.Above
60km,HOxproductionisdominatedbythephotolysISOfH20atLyman-αradiation:
H20+hv→OH+H.
(1.29)
Below60km,theoxidationofH20byO(lD)isthoughttobethemainsourceofHOx:
7
0(1D)+H20→20H.
(1.30)
TheoxidationofmethanebyO(1D)hassomecontributionsasasourceofHOxinthe
lowerstratosphere.Inturn,theremovalofHOxinthestratosphereandmesosphere
OCCurSbyterminationreactionsleadingtotheformationofwatervapororhydrogen
PerOXide[13,14]:
OH+HO2→H20+02
(1.31)
HO2+HO2→H202+02
(1.32)
H+HO2→H2+02.
(1.33)
Production
by
ofOHin
reaction(1.30)isinitiated
the
photolysis
ofO3at
wavelengthshorterthanabout320nmtoproduceO()D)asshowninFigurel.6.Most
oftheO(1D)atomsisquenchedtogroundstateatomicoxygen,0(3p),bycollisionswith
N20rO2,butasmallfractionofO(lD)reactswithH20toproduceOH.Ozone
moleculehashugeabsorptlOnCrOSS-SeCtionsintheUVbetween200and300nm.The
UVabsorptionspectrumreportedbyMalicetetal･[15]isshowninFigurel･3b･There
are
various
ozone
pathwaysfor
thermochemicalthreshold
wavelengths[16].The
have
dissociatiollChannels
photolysis,aSlistedin
been
believed
to
be
Tablel.1along
fo1lowlng
dominantin
the
tWO
their
with
SPln-allowed
photolysIS
OfO3
between230and300nmwithreportedquantumyieldsofca.0.9andO.1[17]:
0,+hv→0(】D)+02(alAg)
(1.34a)
→0(3p)+02(Ⅹ3∑g
).
(1.34b)
Thespinfbrbiddenchannel(1.34c)occursintheUVregionabove300nmaswellas
Charulel(1.34a)and(1.34b):
03+hv→0(lD)+02(Ⅹ3∑g
).
(1.34c)
ProductionoftheO(1D)atomsabove310nmhasbeenattributedtobothchannel
(1.34a)andviainternallyexcitedO3andspin-forbiddendissociationchammel(1･34c)
[18,19].Ataround200nm,Whichcorrespondsto"stratosphericwindow"region,the
twoo(ls)productionchannelsareenergeticallypossibleaslistedinTablel.1:
03+hv→0(1s)+02(X3∑g-)
→0(1s)+02(alAg).
(1.34d)
(1.34e)
Thede-eXCitationofO()s)byN2andO2isveryslowwiththeroomtemperaturerate
coefncientsof<5×10-17and4.0×10･13inunitsofcm3molecule-1s-l,Whilethatof
O(lD)isveryfastwiththeroomtemperatureratecoemcientsof2.6×10.‖and4.0×
10-11inunitsofcm3molecule-1s
1.ThereactionratesofO(lD)andO(ls)withH20do
8
notdifftrmuchfromeachother･Therefbre,theformationofO(1s)fr01nChannels
(1･34dandl･34e)canbeasourceofOHradicalsasshowninFig.1.6.Inthisthesis,
thephotolyticformationofO(ls)fromtheUVphotolysisofO3arOund200nmandits
SubsequentreactionswithsmallmoleculesrelevanttOmiddleandupperatmospheric
Chemistryhavealsobeenreported･ImpactonHOxfbrmationinthestratosphereand
mesospherethroughO(1s)+H20reactionhasbeenreportedinChapter6.
1･4ChemistryofNOintheupperatmosphere
SinceBarth[20]discoveredalargeamOuntOfNOintheupperatmosphere,the
roleofNOinthephotochemistryandthermalbudgetofthelowerthermospherehave
beenrecognized･Theescaplng5･3-PmNOradiationcontributesslgni丘cantlytocool
thethermOSPhere[2]･TheexothermicreactionsinvoIvingoddnitrogenspeciesare
kn0wnaSSOurCeSOfthermosphericheating[2].ThedownWardnowofNOfromthe
lower
thermosphere
to
the
upper
stratosphere
may
cause$1gni丘cantloss
ofO3,
especiallyinthepolarnightregions[21]･ThermosphericNOhasapeakconcentration
typICallyaroundllOkm･SatelliteobservationsshowsthatthepeakNOdensitiesof
∼108moleculescm-3atlO5±2･5kminthelatituderange380N-580S[22].
Thesourcesofthermosphericnitricoxidearethechemicalreactions(1.35)and
(1･36)asshowninFigurel.7:
N(2D)+02→NO+O
N(4s)+02→NO+0,
Whiletherecombinationprocess,
N(4s)+NO→N2+0,
is
the
mainloss
(1.20)
mechanism･Reaction(1.35)is
thought
to
dominate
the
NO
PrOductioninthelowerthermosphere,Whilereaction(1.36),Whoseratecoefncientis
VerytemPeraturedependent,becomesincreaslnglyimportantathigheraltitudewhere
thetemperatureislarger･Thecontributionofreaction(1.36)toNOproductionwas
thoughttobesmallbecausethereactionratefor(1･36)issmallatthetemperatures
encounteredinthelowerthermOSPhere･Atmosphericmodelsincludingthereaction
(1･35)and(1･36)underestimatetheobservedNOdensityinthelowerthermosphere
aroundlO5km[22,23].
Asanadditionalsource,ithasbeensuggestedthatsuprathermal(or′′fast′′or
･･hot･′)N(4s)atomcanreactwithO2tOformNOinthethermosphereatanenergy
9
dependrate,Whichisconsiderablyfasterthanthatatthermalequilibriumfbrgas
temperature[24](Fig･1･7):
(1･37)
払飢N(4s)+02→NO+0.
ThemodelcalculationshaveextensivelybeenperformedtoevaluatethetranSlational
energydistributionsofN(4s)andthefbrmationefnciencyofNOthroughreaction
(1.37)inthethermosphere[24,25,26,27,28]･
Inthethermosphere,nitrogenatoms,N(4s),N(2D),andN(2p),arePrOducedby
aseriesofphotochemicalprocessesinvoIvingthebreakingoftheN2bond[28,29]･
The
direct photodissociation
by
solar photons
between80andlOO
nm
and
by
photoelectronimpactprovidem呵OrSOurCeSOfnitrogenatoms‥
N2+hv→fastN(4s)+N(4s,2D)
(1･38)
N2+e*→fastN(4s)+N(4s,2D,2p)+e.
(1･39)
TheN(4s)atomcarriesexcessenergyandformahotpopulationinthethermOSPhere･
OtherreactionsinvoIvingpositiveions
ormetastable
atoms
also
contributetothe
productionofsuprathermalN(4s)atoms[28,29]･
ThesuprathermalN(4s)atomsfbrmedbytheseprocessessubsequentlyco11ide
withambientmolecules(N2andO2)inadditiontoreaction(1･37)･Thethermalization
crosssectionsofN(4s)withambientgasesarecrucialtoevaluatetheNOformationin
thethermosphere･However,nOlaboratorystudyofthedirectmeasurementsforthe
thermalizationcrosssectionofsuprathermalN(4s)atomswithambientgaseshasbeen
perfbrmed･InthisthesIS,thelaboratoryexperiments
aboutcollisionalrelaxation
processesofsuprathermalN(4s)atomshavebeendescribedinChqpter5･
1.50(1s)airglowintheupperatmosphere
Inrecentyears,agreatdealofaeronomicresearChhasfbcusedonalrglow
emissions,WhicharestudieduslnggrOund-based,rOCketandsatellitetechniques･The
mostfrequentlyobservedemissionistheatomicO(ls)greenlineemissionat557･7nm･
Thisemissionparticularlyprovidestheinfbrmationaboutthevariabilityofsolaractivity
andatomicoxygenconcentrationintheuppermesosphereandthermosphere･
TheBarthmechanismisknowntobethedominantexcitationprocessofthe
nightglowemissionpeakaroundlOOkm[30,31],thatis,
0(3p)+0(3p)+M→02*+M
O2*+0(3p)→02(Ⅹ3∑
g)+0(1s),
10
whereO;iselectronica11yexcitedstate(S)ofoxygenmolecule･Theproductionrateof
O(】s)duetotheBarthmechanismisproportionaltothesquareofthedensityofatomic
oxygen･Consequently,anyChangeintheatomicoxygenconcentrationwoulddirectly
afftcttheO(ls)557.7-nmemission.Therefbre,thenightglowobservationshavebeen
usedtoinvestlgatethetranSPOrtPrOCeSSeSOfatomicoxygeninthelowerthermosphere
[32andrefbrencestherein]･
Recently,thewindimaginginterfbrometer(WINDII)onUpperAtmosphere
ResearCh
Satellite(UARS)[33]has
dataofdayglowemission
extensive
provided
thoughoutthe80to300kmaltitude･The557･7nmdayglowemissionshowstwo
peaksinitsemissionrate,namely,OnearOund150-175kmandtheotheraround90-100
km.Intheemissionpeakaround150-175km,threeimportantprocessescontributeto
theproductionofthisemission:
02++e→0(ls)+0(3p)
(1･42)
N2(A3∑｡+)+0(3p)→N2+0(1s)
(1･43)
0(3p)+e*→0(1s)+e.
(1･44)
Them｡delcalc｡1ati｡nSSh｡WthattherelativecontributionstotheproductionofO(ls)
duetoabovesourceschangewithaltitude[34]･
TheproductionprocessesofO(ls)relatedtotheemissionpeakaround90-100
km
during
recombination
daytlme
process
are
Shownin
ofatomic
Figurel･8･In
oxygen(Barth
this
reglOn,the
mechanism)is
three-body
considered
as
the
importantprocessforO(ls)production･However,theWINDIIdatashowedthatthe
volumeemissionrate(VER)(numberofphotonsemittedperunitsvolumepersecond)
ofthegreenlineemissionwaslargerbyafactorofthreeormoreinthedaytimethanat
night[35,36,37].Theobservationindicatesthatfurtherexcitationprocessesshouldbe
invoIvedinadditiontotheBarthmechanism.Shepherdandco-WOrkers[35,36,37]
haveproposedthatphotodissociationofO2bythesolarradiationbetw占enlOOand130
nm,eSPeCiallyatLyman-β(102･6nm),isaprimarysourceofO(1s)fbrtheemission
peakaround90-100kminthedaytime･Inthisthesis,theimpactofthe
formationofO(ls)fromtheUVphotolysisofO30nthegreenlinedayglowemission
hasbeendescribedinChapter6.
11
direct
H20
N20
CFC
Emission
ヽ
ノ芦
Figurel･1･Representation
ofthe
couples
processesinthemiddleatmosphere[3]･
12
chemical,radiative,and
dynamical
/
0.2
0.4
0.6
0.8
1.O
FractionaIcontribution
Figurel･2･FractionoftheoddoxygenlossrateduetotheChapmanmechanismand
HOx,NOx,andC10xcycles(basedonamid-1atitudediurnalaveragecalculation)[1]･
13
l
OU
(Tむ一⊃U苫∈N∈U)uO葛軍SS｡｣Uu｡喜｡Sq<
1 O■
19
1 0-
20
1 0-
21
1 0-
22
1 0■
17
1 0■
18
1 0-
19
1 0■
lb
20
200
250
300
WaveIength(nm)
Figurel.3.Absorptionspectrumofa)N20andb)03intheultravioletregionat298K,
inwhichthecross-SeCtiondataofN20andO3WeretakenfromSanderetal.【11]and
Malicet[15],reSPeCtively.
14
(T2uTSNI∈USuO}○量×⊃正｣苫S
Figurel･4･Solarphotonfluxesataltitudeof50,30,andOkm,reSPeCtivelyabove
earthsurfacesasafunctionofwavelengthforUSstandardatmosphereatsolarzenith
angle(SZA)of500･
15
Figurel･5･SchematicsofthefateprocessesofN20inthestratosphere･The･ratios
ofeachsinkarealsopresented･
16
Figurel･6･SchematicsofthereactionpathwaysinvoIvingOHproductioninthe
middleatmosphere(SeeteXt)･
17
Figurel･7･SchematicsofthereactionpathwaysinvoIvingNOproductioninthelower
thermosphere(SeeteXt)･
18
+hv?
■ ■
■
t
=
=
■
▲
557.7nm
em)SSLOn
Figurel.8.SchematicsofthereactionpathwaysinvoIvingO(1s)productioninthe
lowerthermosphere(SeeteXt)･
19
Tablel.1.Thermochemicalthresholdwavelengthsfbrphotodissociationpathwaysof
O3,inunitsofnm.
02(X3=g-)02(al△g)02(b)=g+)02(A3=u+)02(B3=u-)20(3p)
0(3p)1180
460
230
0(lD)
410
260
167
0(ls)
234
179
129
20
RcferencesfbrChapterl
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2000.
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[3]Brasseur,G.P.,Orlando,J･J･,Tyndall,G･S･,Atmo3PhericChemLsiTyandGlobalChange,
OxfbrdUniversityPress,NewYork,1999･
【4]Chapman,S.,Aゐm･Rqy肋teo7d･Soc･,3,103(1930)･
[5]Bate,D.R.,Nicolet,M･,JGeqp7p･Res･,55,301(1950)･
[6]Crutzen,P.J.,Q.JR･肋teorol･Soc･,96,320(1970)･
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[8]Stolarski,R.,Douglass,皐･R･,JCan･Chem･,52,1610(1974)･
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Moortgat,G･K･,Ravishankara,A･R･,Kolb,C･E･;Molina,M･J･,Finlayson-Pitts,B･J･,
ChemicalKinelicsandPhotochemicalDataPruseinAtmo軍hericStudies,Evaluation
No.14,JPLPublicationO2-25,2003･
【12]Okabe,H.,PhotochemistTyQrSmallmolecules,Wiley-Interscience,NewYork,1978･
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Company,Dordrecht,Holland,1986･
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Ge甲/叩.月e∫.エe払,27,2613(2000)･
[15]Malicet,J.,Daumont,DっCharbonnier,J･,Parisse,C･,Chakir,A･,Brion,J･,JAtmos･Chem･
1995,2ノ,263.
【16]Atkinson,R.,Baulch,D.L･,Cox,R･A･,HampsonJnR･F･,Ken.,J･A･,Rossi,M･J･,Troe,J･,
Jタわげ.C力e批点げ加叫27,1329(1997)■
[17]Matsumi,Y,Kawasaki,M･,Chem･Rev,103,4767(2003)･
[18]Tbkahashi,K.,Kashigami,M･,Matsumi,Y,Kawasaki,M･,OrrEwing,A･,JChem･P卸s･,
105,5290(1996).
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[20]Ba11h,C.A.,JGeqp7p･Res･,69,3301(1964)･
[21]Solomon,S.,R.RGarcia,Planet･勘ace･Sti･,32,399,(1984)･
[22]KrishnaKumar,C.,Swaminathan,P･K･,Anderson,D･E･,%e,J･H･,Gul-SOn,M･R･,
Abrams,M.C.,JGeqpjvLS.Res.,100,16,839(1995)･
[23]Suskind,D.E.,Strickland,Meier,R･R･,旬eed,T･,Fparvier,JGeqpわ岱･Res･,100,19,687
(1995).
[24】SololⅥ011,SリアJα〃eJ･勒αCe助f･,31,135,(1983)･
【25]Lie-Sevelldsen,0.,Rees,M･,Stamnes,K,Whipple,E･C･,Pla71et･勘aceSti･,39,929,
2l
(199り.
【26]G6rard,J.C.,Bisika)0,D･V･,Shematovich,ⅤⅠ･,DuffJ･W･,JGeqpjw･Res･,102,285,
(1997).
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DeM往iistre,R.,Yee,J.H.,Paxton,L･,Anderson,D･E･,Strickland,D･J･,Du托J･W･,J
Ge甲砂∫.月e∫.,103,11579(1998)･
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18549(2000).
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[30]Barth,C.A.,Ann.PjD}S･,5,329(1964)･
[31]McDade,1.C.,Murtagh,D.P.,Greer,R･G･H･,Dickinson,P･H･G,Witt,G･,Stegman,J･,
Llewellyn,E.J.,Thomas,L.,Jenkins,D･B･,Planet･勘aceSti･34,789(1986)･
[32]Zha11g,S.P.,Roble,R.G･,Shephered,G･G･,JGeqp7p･Res･,106,21,381(2001)･
[33]Shepherd,G.G.,etal.,JGeqpj叩･Res･,98,10,725(1993)･
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22
Chapter2
Experimental
2.10verviewofthedetectiontechniquesofN(4s)andO(1s)atoms
2.1.1I)etectiontechniquesofN(4s)atoms
TherearethreeelectronicstatesforthegroundstateconngurationsofNatom:
N(4s,/2),N(2D5/2,3/2),andN(2plr2,3佗)withtheirrespectiveenergiesofO,2･38and3･58
ev.Inthepreviousexperimentalstudies,maSSSPeCtrOmetryteChnique[e･g･1,2,3]
andresonantnuorescenceteclmique[e.g.4,5,6]around120nmwereusedfbrdetection
ofthe
electronic
groundstateN(4s)atoms.The
experimentalsetupreportedby
BrunningandClyne[3]isshowninFigure2･1a･Intheirstudy,theN(4s)atoms
generatedinamicrowavedischargeofN2WeremOnitoreduslngaquadrupolemass
spectrometerwithachannelmultiplier･TheexperimentalsetupreportedbyAnderson
andco-WOrkers[5,7]isshowninFigure2.1b.Intheirstudy,theresonantfluorescence
丘omtheN(2p23s4pl′2,3/2,5′2→2p34s2/3)transitionsarOund120nmwasdetectedusing
anatOmicnitrogenlampandaphotomultiplier,inwhich,theN(4s)atomswere
generatedinamicrowavedischargeofN2･Theresonanceabsorptiondetectionsof
N(4s)atomsatl19.9nmwithanatOmicnitrogenlampwerealsoemployed[8,9]･
Recently,Adamsetal･[10]demonstratedthetwo-PhotonLIFdetectionofN(4s)at207
11mWhichisresonanttothetwo-PhotonN(2p23p4s,/2←2p34s2/3)transition,inwhich
theN(4s)atomswereproducedbythephotolysisofN20at207nm･
Inthisthesis,aneWteClmiqueforhigh-SenSitivedetectiontechniqueofN(4s)
uslngVUV-LIF
spectroscopy
at120･07nmwhichisresonantto
the
one-Photon
N(2p23s4p3/2←2p34s2/3)tranSitionhasbeendeveloped･
2.1.2DetectiontechniquesofO(1s)atoms
Therearethreeelectronicstatesforthegroundstatecon丘gurationsofOatom:
0(3po,l,,),0(lD2),andO(lso)withtheirrespectiveenergiesofO-0･028,1･97and4･19
ev.IncontrasttothenrstelectronicexcitedO(1D)atohl[11,12],thereislittle
infbrmatiol-aboutthephotochemicalpropertiesofO(ls)atom.Oneofthepossible
reasollSforthissituationisadifncultytodetectO(ls)atomssensitively.Inprevious
23
laboratorystudiesonthephotochemicalreactionsinvoIvingO(ls)atoms,detectionof
thevisibleemissionat557･7nmcorrespondingtothels-1Dtransitionwasusedfor
InOnitoringO(】s)atoms[e.g.13,14,15].Duetotheorbitallyfbrbiddennatureofthe
ls.1Dtransition,thesensitivityoftheO()s)emissiondetectionmethodsh｡uldbe
relativelylow･TheexperimentalsetupreportedbyYoungetal.[13,16]isshownin
Figure2･2･Intheirstudies,theO(1s)atomsgeneratedinthenushphotolysisofN20
at147nm(XelamP)weremonitoredusingtheO(1s→lD)emissionat557.7nm.
Inthepresentstudy,aneWteClmiquefbrhigh-SenSitivedetectiontechniqueof
O(ls)usingVUV-LIFspectroscopyat121･76nmwhichisresonanttotheone-Photon
O(2p33sllp)←2p41so)tranSitionhasbeendeveloped･Thereby,Photochemical
reactionsinvoIvingO(1s)atomhavebeenexamined.
2･2VUV-LIFspectroscopy
2.2.1PrincipleofLIFmethod
TheLIFteclmique,nrStPrOVidedbyZareandco-WOrkers[17],isapowerfu1
toolfordetectionoftraceamountsofatomsormolecules.ThebasicideaofLIFisas
fo1lows･Light丘omatunablelaserimplngeSOnthesampletobeinvestigated.As
the凸-equenCyOfthelaserchanges,atOmS(molecules)withintheirradiatedportionof
thesamplewillbeexitedtonuorescencewheneverthespectralenvelopeofthelaser
OVerlapsanabsorptionlineoftheatom･Theemissionisdetectedbyaphotomultiplier,
Which′′view′′theexcitationzone･Thefluorescenceintensityisrecordedasafunction
Oflaserwavelengthtoproducewhatweca11anuorescenceexcitationspectrum.The
intensitiesarethenconvertedtorelativepopulationsofthevariousinternalstates,With
theinformationofvibrationalandrotationalintensltyfactors.
Inorderforatomtobedetectablebylaser-inducedfluorescence,thereare
three
m往IOr
requlrement
factors.First,the
that
oneis
obvious
atomfluoresces.
Moreover,itispreferablethatthequantumyieldfornuorescenceprocessisunityso
thattheconversionoffluorescenceintensitiestopopulationsisnotcomplicatedbyother
internalstates･Second,the
band
system
was
spectroscopICa11y
analyzed
so
that
quantummemberscouldbeasslgnedandintensityfactors,SuChaslinestrengthfbrthe
transitiol一,COuld
be
obtained･Third,the
atoms
band
systemis
availabletunablelaserlight･Recentdevelopmentofthetechniquestogeneratetunable
VUVlaserlightishelpfu1forthisrequlrement.
24
accessiblewith
2.2.2PrincipIeofVUVlaserlightgeneration
Inthepastfbwyears,Photochemicalprocesseshavebeeninvestigatedinour
laboratoryusingthecoherentVUVradiationtodetectatomsandradicalssuchasH(2s),
S(lD),S(3pj),0(1D),0(3pj),Cl(2n),ClO,and
teclmology
tunable
developed
coherent
a
newlight
VUV
sourceinthe
wavelength
by丘･equenCylnlXlngln
generated
radiation
CO【18,19,20].Therecentlaser
reglOn,Whichis
the
gases
and
vapors.
SincetheearliestexperimentsbyWardandNew[21],therehasbeenmucheffbrtto
developnewmixingschemesaboutthirdharmOnicgeneration(THG)andtwo-Photon
resonantfour-WaVemlXlngPrOCeSSforextendingthelaser-basedlightrangetotheVUV
and
even
to
the
near
X-ray
fbur-WaVe
CategOries,namely
mlXlnglS
reglOn.Thefour-WaVe
two
Classi丘edinto
dif托rent
Sum丘equencymixing(SFM)andfour-WaVe
frequencymixing(DFM).ThewavenumbersofthegeneratedVUVlight(0)vuv)for
theSFMandDFMcanbewritteninfo1lowlngform:
(2.1)
Ovuv=2(Ol±の2,
the
Where(Dlis
wavenumber
nrstlaserlight(0)11aser),Which
ofthe
two-Photonresonancelevelofthe
non-1inearmedium,and
tunablelaserlight(0)21aser),Whose
variations
tuned
are
o2isthatofthe
capable
to
the
second
ofobtainingfrequency
tunabilitylnOvuv.Whilekeeplngtheresonanceconditionbytunlngthewavenumber
Oftheollaserlight,Varylngthewavenumberoftheo)21aserlightmakesitpossibleto
generate
thefrequency
tunable
VUVlight.Theoretically,the
generated
power
VUVradiation,Pvuv,forthefbur-WaVemlXlnglSglVenby
(2.2)
且.tv∝Ⅳ2ズ昌)月2ろダ匝l△た,∂),
WherePlandP2aretheinputpowersofo)1ando)21asers,Nistheatomicdensityof
non-1inearconversionmedium,X(3)isthethirdordernon-1inearsusceptibilityperatom.
Fisthephasematchingfactordependingonbl△kandb=bl/b2.Here,b)andb2are
the
confbcalparameterS
Ofthelaser
beams,and△kis
the
wave
vector
mismatch
betweenthegeneratedradiationanddrivingpolarization[22]:
△た=んuv-(2んl±ち).
THG
(2.3)
andfour-WaVemixingininertgases(forexample,Xe,Kr,Ar)have
beenwellstudieduslngagaSCellorsupersonicrategasjetforbroadlytunableVUV
radiationinthewavelengthrange(入=110-200nm)[23,24,25].Inaddition,metallic
25
of
VaPOrS(forexample,Sr[26],Mg[27],Zn[28],Hg[29,30])aregoodcandidatesfor
generatlngVUVandnearX-raylights･Inthisthesis,theSFMintheHgvaporandthe
DFMintheKrgaswereusedtogenerateVUVlightarOund120･1and121.8n皿,
respectively.
2･2･3PrincipleoftheDoppIerprofilemeasurement
TheDopplerpromemeasurementsofthephotofragmentshavebeenwidely
usedtoinvestigatechemicalreactionsandphotodissociationprocesses[e.g.31,32].
AnalysISOftheDopplerpronleprovidestheinfbrmationaboutthekineticenergyof
atoms･Theshiftinfrequencyofradiation(△v)emittedbyanatommoving
with
Velocity(v)atangleO=Obetweenthedirectionofthemotionofatomsandlineofsight
OftheobserverisglVenby
Vo
△v=
(2.4)
l+V/c'
Wherecisthevelocityoflight,Voisresonancecenterfrequencyofatomictransition.
The丘equencyshiRsofatomsawayfromlinecenteroftheexcitationtransitionofthe
LIF
process
depend
the
on
velocity
components
ofatoms
along
the
propagation
directionoftheprobelaser[33]･ThethermalDopplershapesfo1lowaBoltzman
distributionofvelocities･TheDopplershi氏(△vT)fbrgiventemperature(T)canbe
Calculatedby
工1｡211′2,
慧1n2)
△vT=苧(
C
＼
m
(2.5)
WherekBistheBoltzmanconstant,misthemassoftheatom.
TheobservedDopplerpro丘1eisalsobroadenedbytheVUVprobelaserline
Width･AssumlngtheGaussianshapeforprobelaser,theVUVprobelaserlinewidth
(△vlaser)canbeestimatefromtheobservedDopplerslli氏(△v｡bs)ofthethermalized
atoms:
(△v｡bs)2=(AvT)2+(Av.aser)2.
2･3
(2.6)
Experimentalsetup
Inthepresentstudy,theformationofN(4s)inthephotolysisofN20,NO,and
NO2at193nmandthereactionskineticsinvoIvingN(4s)havebeeninvestigatedusing
26
vuv-LIF
detection
technique
ofN(4s)atoms･The
fbrmatiol-OfO(ls)inthe
photolysisofO3at193,215,and2201一皿andreactionkineticsinvoIvingO(ls)have
alsobeeninvestigatedusingVUV-LIFdetectiontechniqueofO(1s)atoms･Figure2･3
and2.4showschematicdiagramSOfourexperimentalarrangementsfbrdetectingN(4s)
andO(ls),reSPeCtively.TheexperimentalarrangementSincludeareactionchamber,gaS
inletsystem,PhotolysISandprobelasersystem,andadataacquisitionsystem･The
microwave(MW)dischargeandtitrationsystemarealsodepictedinFig･2･3･
2.3.1
Reactionchamberandflowsystem
Thereactionchamberwasmadeofstainlesssteelwiththesize80×80×80
mm,andwascontinuouslyevacuatedbyarotarypump(AIcatelmode12021,330Liter/
min.)throughaliquidN2traP･Thetotalgaspressureinthereactionchamberwas
measuredbyacapacitancemanometer(MKS,Baratoron122AA)･Samplegaseswere
suppliedintothechamberthroughpoly-tetrafluoroethylenetubing･Thenowratesof
samplegaseswereregulatedbyneedlevalvesormassflowcontrollers(MFC)(STEC,
SEC-400MK3).
2.3.2
Photolysislasers
ThephotolysISradiationat193nmwasobtained丘omanArFexcimerlaser
(LambdaPhysik,COMPexlO2)･Thetunablephotolysisradiationbetween215and`220
nmwasobtainedbyanNd:YAGlaserpumPedopticalparametricoscillator(OPO)1aser
(Continuuln,Powerlite8010andPantherOPO)andasubsequentfrequencydoublingina
β-BaB20.(BBO)crystal･TheOPOlaserwavelengthwascalibratedbyintroducinga
partoftheOPOsigna11ightintoawavemeter(Burleigh,WA-4500)･Dichroicmirrors
wereusedtoseparatethefundamentalandUVoutputs･TypicalpulseenergiesofdleUV
photolysISradiationwerelO,0･7,andl･OmJat193,215,and220nm,reSPeCtively･
2.3.3
TunableVUVlaserfbrdetectionofN(4s)atoms
FordetectionofN(4s)atomsbytheVUV-LIFmethod,theatomiclineofthe
N(2p23s4pl/2←2p34s2/3)transitionat120･07nmwasused･TheprobeVUVlaser
radiation
was
generated
bytwo-Photonresonantfbur-WaVe
SumfrequencymlXlng
(ovuv=2ol+0)2)inHgvapor[29]･Energyleveldiagramoftherelevantatomic
levelsofHgwasshowninFigure2･5a･Twodyelasers(LambdaPhysik,Scanmate2E
27
andFL3002E)weresimultaneouslypumpedbyasingleXeClexcimerlaser(Lambda
Physik,COMPex201)･OnedyelaseroperatingwithRhodaminlOldyeinMeOH
soIvent
generated4-5mJ/pulse
around625n皿･The
visible output
was
鮎quency-doubledil-aK=2PO4(KD'p)crystaltoobtain312･76nmwhichistwo-Photon
resonantWithHgelectronictranSition(6s7sIso←6s21so)･Theoutputofotherdyelaser
operatingwithCoumarin307dyeinMeOHsoIventproduced2-4mJpulse-1ar0und517
nm.ThetwolaserbeamSWereCarefu11yoverlappeduslngadichroicmirrorandfocused
intotheHgvaporcellwithafusedsilicalens(f=250nm)･TheRydbergtransitionsof
Hg(6s115pllpl←6s2Iso)andHg(6sl15p13pl←6s21sb)wereusedforthegeneration
oftheVUVradiationaround120.1nm.
Figure2･5bshowsaschematicdiagramoftheHgvaporcellusedinthisstudy
togeneratevuvlaserlightaround120･1nm･AthinLIFwindowwasusedto
separatetheHgvaporcellandreactionchamber･Inordertopreventthedepositionof
Hgvaporonthewindows,WaternOWSWerePreParedbetweenaheaterandwindows･
ThetemperatureintheHgvaporcellwascontrolledaround450-470Ktoobtain
enoughVUVprobelaserpowerforexperiments,Whichcorrespondstotheequilibrium
Hgvaporpressureof8-14Torr[34]･KrwasaddedintheHgvaporcellforphase
matchingandtheoptlmumPartialpressurewas6-8Torr･Experimentally,Krwas
addedintotheHgce11pr10rtOheatlngandsometimesre丘11edaftercoolingthece11
down.ThegeneratedVUVlaserlightwasintroducedintoareactionchamberthrougha
LiFwindow.A丘actionoftheincidentVUVlightpassedthroughthereactionchamber
wasrenectedbyathinLiFplateheldintheendofthereactionchamberandledintoaNO
photoionlzationcell･TherelativeintensityofVUVlaserlightwasmonitoredby
measurlngthephotoionizationcurrent･TypicalNOgaspressurewas2-3Torr･The
vuvlaserline
width
was
estimatedto
be
O.40cm-1fu11-Width-at-half-maXimum
(FWHM)withaGaussianshape,WhichwasestimatedfromtheDopplerprofileof
thermalizedN(4s)atomsproducedfrom193-nmlaserirradiationofNO2inthepresence
of3.6Torrofheliumatadelaytimeof5psbetweenthephotolysisandprobelaser
pulses.TheN(4s)detectionlimitoftheVUV-LIFsystemwasestimatedtobe2×109
atomscm-3.
2.3.4
恥nableVUVlaserlbrdetectionofO(ls)atoms
FordetectionofO(ls)atomsbyVUV-LIFmethod,theatomiclineofthe
28
0(2p33s】lpl←2p41so)transitionat121.76nmwasused.TheprobeVUVlaser
radiationwasgeneratedbytwo-Photonresonantfbur-WaVedifftrencefrequencymixlng
(ovuv=20)1-02)inagasmixtureofKr/Ar[25]･Energyleveldiagramofrelevant
atomiclevels
ofKr
was
Figure2.6a.Two
shownin
dyelasers(Lambda
Physik,
Scarmlate2EandFL3002E)weresimultaneOuSlypumpedbyasingleXeClexcimerlaser
(LambdaPhysik,COMPex201).Theoutput丘omonedyelaseroperatingwithBis-MSB
dyeinl,4-dioxaneSOlutionwas丘equency-doubledbyaBBOcrystaltogenerateUVlaser
at212.56nm,Whichwastwo-PhotonresonantwithKr5p[1/2]0.Theoutput丘omthe
solutionwasaround840nm･
otherdyelaseroperatingwithStyryl-9MdyeinDMSO
O.4and4mJfortheUVandnear-IRlaserpulses,
Thetypicalpulseenergieswere
respectively･Thelaserbeamswerecarefu11yoverlappeduslngadicl-rOicmirrorand
focusedintotheKr/Arcontainingcellwithafusedsilicalens(f=200mm)･
Figure2･6b
shows
a
schematic
diagramOfthe丘equency
conversion
cell
includingKr/ArgasmixturetogenerateVUVlaserlight･AthinLIFwindowwas
usedtoseparatethecellandreactionchamber･Arwasaddedfbrphasematchingand
the
optimum
partialpressures
ofKr
Ar
and
were15-20andlOO-120Torr,
respectively.TheVUVlaserlinewidthwasestimatedtobeO･48cm-1(FWHM)witha
GaussianShape,Whichwasestimated丘omtheDopplerpro丘1eofthermalizedO()s)
atomsproduced丘om193-rmlaserirradiationofO3inthepresenceof2Torrofhelium
atadelaytimeof3トSbetweenthephotolysisandprobelaserpulses･TheO(1s)
detectionlimitoftheVUV-LIFsystemwasestimatedtobe3×108atomscm-3･
2.3.5
Detectionsystemanddataacquisition
TherepetitionrateofthephotolysISandprobelasersystemwaslOHz･The
timedelaybetweenthephotolysISandprobelaserpulseswascontrolledbyadigitaldelay
generator(StanfordResearChSystems,DG535),andcheckedontheoscilloscopeusing
twofast-reSPOnSeSilicon-Photodiodedetectors(HamamatSuPhotonlcs,S1722-02)･The
jitterofthedelaytimewaslessthan10ns･TheVUV-LIFsignalsfromN(4s)andO(1s)
atomsweredetectedusingasolarーblindphotomultipliertube(PMT)(EMR,542J-09-17),
whichhadanMgF2WindowandKBrphoto-Cathodethatwassensitiveonlybetweenl18
and150run.Abandpass丘1ter(ActonResearCh,mOde1122-VN,九=122nm,A入=12
1Ⅶ1)wasinstalled.TheobservationdirectionoftheLIFwaspelPendiculartobothVUV
probeandphotolysISlaserlight,andperpendiculartOtheelectricvectoroftheVUV
29
probelaser･Theoutputofthephotomultiplierwaspre-amPli五edandaveragedoverlO
laserpulsesbyagatedintegrator(StanfordResearchSystems,SR-250),andthenstored
on
a
personalcomputer･The
outputfrom
the
NOionization
pre-amPlinedandaveragedoverlOlaserpulsesbyanothergated-integrator,andstored
Onthepersonalcomputer･
30
cellwas
also
(a)
COLDTRAPS
(b)
Figure2･1･SchematicdiagramsoftheN(4s)detectionsystemusing(a)themass
spectrometry[3]and(b)theresonantfluorescenceteclmique[5,7]･
31
ToPump
l〃00d,s Horn
Figure2.2･SchematicdiagramOftheO(1s)detectionsystemusingaO(ls→lD)
emissionat557.7nm[13,16].
32
Figure2･3･SchematicdiagramofourexperimentalapparatusfordetectingN(4s)
atomswiththeVUV-LIFtechnique･MFC,maSSflowcontroller;PMT,Photomultiplier
tube;KD*p,KH2PO4CryStal･
33
Figure2.4.SchematicdiagramofourexperimentalapparatusfbrdetectingO(ls)
atoms
with
the
VUV-LIF
teclmique･OPO,OPticalparametric
photomultipliertube;BBO,β-BaB204CryStal･
34
oscillator;PMT,
(a)
(L.∈Um≡)岳｣心⊂むuO10左
0
(b)
300mm
100mm
LiFWindow
QuartzWindow
K｢gasl
EIectricHeater
山vu,
■■■
■lll■-
◆-
†
WaterfLow
COOler
巳
ロ
′
Hgreservoi
r｣
ロ
6
I
l
6
Reaction
Chamber
Lens
(f=250mm)
Figure2･5･ThegenerationschemeofVUVlaserradiationbytwo-Photonresonant
fbur-WaVe
Sumfrequency
mixinginHgvapor･(a)EnergyleveldiagramOfthe
relevantatomiclevelsinHgforVUVgenerationaround120･111m･(b)Schematic
diagramofHgvaporcell(SeeteXt)･
35
(a)
㌻∈UE≡)岳｣心⊂心uO10エd
ハU
(b)
:70mm:
r←･>:く
l
>:
l
LiFWindow
QuanzWindow
仙∨
竿十
†
:
200mm
■■■■■■■l■
国
KrandArgases｣
Lens
Reaction
(f=200mm)
Chamber
Figure2･6･ThegenerationschemeofVUVlaserradiationbytwo-Photonresonant
four-WaVedi脆rentfrequencymixlnglnagaSmixtureofKr/Ar･(a)Energylevel
diagramoftherelevantatomiclevelsinKrforVUVgenerationaround121･8nm･(b)
SchematicdiagramofKrcell(SeeteXt)･
36
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[30]Tbmkins,F.C.,Mahon,R･,qブt･Letl･,7,304(1982)･
[31]Houston,P.L.,JPb}S･Chem･,91,5388(1987)･
[32]Matsumi,Y,Das,P.K.,Kawasaki,M･,JChem･P如･,92,1696(1990)･
[33]Zare,R.N.,Herschback,D･R･,Proc･LEEE,51,173(1963)･
【34]Smith,A.V.,Alfbrd,W･J･,Jqフt･Sbc･Am･B,4,1765(1987)･
38
Chapter3
N(4s)fbrmationintheUVphotolysisofN20
anditsimplicationsfbrstratosphericozonechemistry
3.1Introduction
N20isanimportantatmosphericminorconstituentasthemainsourceofNOx
in
the
stratosphere,Since
NOx
the
species
play
a
slgnincant
rOlein
themiddle
atmosphericchemistry･MostoftheN20tranSPOrtedthroughtheplanetaryboundary
layerandthe丘eetropospheretothestratosphereisphotolyzedatUVwavelengthsto
O(lD)+N2,Whileasma11丘actionofN20reactswithO(lD)atoms:
N20+hv→N2+0(]D)
(入<341nm),
N20+0(lD)→2NO
→N2+02.
TheN20photolysisaround200n皿isconsideredtoproceedthroughchannel(3.1a)
Withanalmostunityquantumyield[1]andtheotherenergeticallyavailablechannels
areveryminor:
N20+hv→N(4s)+NO(X2口)(入<248nm)
(3.1b)
→N2+0(3p)
(入<742nm)
(3.1c)
→N2+0(ls)
(入<211nm)･
(3.1d)
Felderetal･[2]studiedthedissociationdynamicsofN20at193nmbyphoto丘agments
translationalspectroscopyandreportedthatchannel(3.1b)was
unimportantasthe
time-0用ightsignalintensltyatm/e=30waslessthanthedetectionlimit.Greenblatt
andRavishankara[3]reportedtheupperlimitvalueofthequantumyieldforcharmel
(3･1b)inthe193nmphotolysisofN20tobe8×10.3throughthechemiluminescent
detectionofNOproducts･Recently,Adamsetal.[4]detectedtheN(4s)fbrmationin
the207nmphotolysIS
OfN20bymeansoftwo-PhotonabsorptionLIFteclmique
(TALIF)usingthesamefbcusedlaserbeamat207nm.Theyhavenotmeasuredthe
quantumyieldforN(4s)formation･ItisdifBculttoestimatethequantumyield丘om
theexperimentsuslngaOne-COlorfocusedlaserbeamfbrbothphotolysISandprobe･
AlthoughtheoxidationofN20byO(1D),Channel(3.2a),isthoughttobethe
dominantglobalsourceofNOinthestratosphere,thephotodissociationreactionisa
39
mqjorremovalprocessofstratosphericN20andtheO(lD)reactionisminor.Asimple
calculationcanpredictthataquantumyieldofl%fbrchannel(3.1b)inN20photolysis
wouldrepresentanapproximateincreaseof15%intheactivenitrogenproductionrate
intheupperstratosphere.Therefore,aPreCisedeterminationofthecharmel(3･1b)
quantumyieldisessentialforevaluatlngthestratosphericNOproductionrate･
Inthis
Chapter,1aboratorystudies
ontheN(4s)atomfbrmationfromthe
PhotolysISOfN20at193nmhasbeencarriedoutuslngateChniqueofVUV-LIF･The
quantumyieldforN(4s)fbrmationwasdeterminedtobe(2.1±0.9)×10,3.The
atmosphericsignincanceofchannel(3･1b)asanewsourceofNOinthestratosphereis
alsodiscussed.
3.2Experimental
ThedetailsoftheapparatususedinthepresentstudyareshowninChapter2
andhereonlyadescriptionrelatedtothischapterisgivenhere.TheN(4s)atoms
PrOducedfromN20photolysISat193nmwereprobedbytheVUV-LIFmethodat
120.07nm,WhichisresonantWiththeelectronictransitionofN(2p23s4pl′2←2p34s2n).
TheCl(2pl/2)atomsproducedfromHCIphotolysisat193nmweredetectedbythe
VUV-LIF
teclmique
associated
at120.14nm,Whichis
with
electric
transition
of
Cl(3p44s2D3r2←3p52p./2).ThetunableVUVlaserradiationaround120.14nmwas
alsoobtainedwiththesameexperimentalsetupfortheVUVlasersystemwiththeHg
VaPOrCellandthenuorescencedetectionsystem･
N20(>99.9%,TakachihoCo.)oragasmixtureofHCl(>99.9%,Sumitomo
Seika)andAr(>99.999%,NihonSanso)(12.3%ofHClinAr)wassuppliedintothe
reaction chamberthrough
mixture
of HCl/Ar
aneedle
valve.Thetypicalpressure
ofN20and
a
gas
were500-900and160-430mTorr,reSPeCtively.While
scarmingtheVUVlaserwavelengthforN(4s)and
Cl(2pl/2)atomdetections,the
reactantspressurewaskepttobeconstant･Itshouldbenotedthathighsensitivityof
theVUV-LIFtechniquemakeitpossibletodetectN(4s)atomsatlowgaspressuresand
shollpump-PrObedelaytime(≦150ns),andthatchemica1lossesthroughsecondary
reactions,forexample,N+N20,N+NOandN+02,Canbesafblyignored･
InthetitrationexperilnentStOCalibratetheabsolutesensitivityoftheVUV-LIF
system,N(4s)atomsweregeneratedbytheMW(2450MHz)dischargeofpureN2gaS
(>99.9%)inanowtube(Pylex,13.7mmi.d.)asshowninFig.2･3.Acoaxialnow
40
tubewasconnectedbetweentheN2dischargenowtubeandtheVUV-LIFchamber･
NO/Argasmixture(0･0268%ofNOinAr)wasintroducJedthroughtheinneriniection
tube(Pylex,3.8mmi.d.),Whichcanmovealongtheouternowtube･Allexperiments
WerePerformedatroomtemperature･
3.3Results
Figure3･1showsthenuorescenceexcitationspectrafbrN(4s)atomsproduced
inthe193nmphotolysisofN20･Theatomiclinepro丘1esoftheN(4pl′2←4s2/3)
transitionweredirectlyobservedbytheVUV-LIFmethodarOund120･07nm･The
dependenceoftheLIFsignalintensityfortheN(4s)atomsonthephotolysislaserpulse
isshowninFigure3･2･WealsocheckedthatnoN(4s)atomssignalwasdetected
without193nmphotolysislight･Theseresultsindicatethatmultiphotonabsorption
processesat193nmordissociationofparentmoleculesbytheprobelaserbeams(Ovuv,
o)ando)2)aresafblyignoredinthiswork･ThequantumyieldforN(4s)formation
fromN20at193nmphotolysiswasdeterminedbycalibratlngthesensitivityofthe
VUV-LIFsystem･Thetwomethodswereusedtoestimatetheabsolutesensitivityof
thedptectionsystemforN(4s)bytheVUV-LIFmethod･Oneisthetitrationteclmique
fortheN(4s)atomconcentrationusingchemicalreactionwithNO･Theotheristhe
comparisonbetweentheLIFintensitiesoftheN(4s)atomsproducedintheN20
photolysisat193nmandCl(2pl/2)atomsproducedintheHCIphotolysisat193nm･
TheCl(2pl′2)quantumyield丘omthephotolysisofHClat193nmhasalreadybeen
reported[5]･
3.3.1ChemicaItitrationmethod
TheconventionaltitrationteclmiquefbrNatomswasusedtocalibratethe
vuv-LIFsystemfordetectingN(4s)atoms[6]･TheN(4s)atomsweregeneratedina
MWdischargeofpureN2gaSandwerethenintroducedintotheVUV-LIFchamber
throughthecoaxialflowtube･WhilemonitoringtheVUV-LIFsignalofN(4s)atoms
at120.07nm,NOmoleculesdilutedwithArwereirjectedintotheflowsystem･The
N(4s)atomswereconsumedbythefo1lowingreaction:
N(4s)+NO→N2+O
k3.3298=3･0×10-11cm3molecule-1s-l,(3･3)
wherek3.3298showsistherateconstant(3.3)at298K[7]･BymonitoringtheLIF
slgnalintensitiesasafunctionofthenumberdensltyOfNOmoleculesadded,the
41
sensitivltyOftheVUV-LIFsystemforNatomdetectionwascalibrated･AtypICal
titrationplotisshowninFigure3･3,inwhichthemassflowrateofNO/Armixturewas
variedbetweenO.6and2.3sccmwhilethetotalflowratewaskeptcollStant(19sccm)･
Whena11theNatomsproducedbytheMWdischargeareconsumedbyreaction(3･3),
theNO
concentration
corresponds
to
theinitialN
atom
concentration･Thus,the
atomsdetectedbytheVUV-LIFmethodwasobtained･
absoluteconcentrationofN
TheinnerNOinjectiontubeismovablesothatthereactiontimecanbevariedby
changlng
thelocation
ofthe
addition
NO
ofthe
check
molecules･To
the
wall
reactivityofN(4s),thetitrationexperimentswerecarriedoutunderdiffbrentresidence
time
conditions(0.2-0.5s)by
oftheNOirdection･No
changingthelocation
was
ofN(4s)atoms
signi重cantinnuencefromthewall-loss
observed,Whichis
consistentwiththeverylowwallreactivityreportedbyWennbergetal･[8]･
Fluorescence
excitation
spectrafor
N(4s)atoms
producedin
the
N20
photolysISat193nmandtheMWdischargeofN2WeremeaSuredtodeterminethe
quantumyieldforN(4s)formationintheN20photolysis･TheN(4s)production
quantumyieldfromthephotolysisofN20isdennedbythenumberdensityofN(4s)
atomsproducedfromthephotolysisdividedbythenumberdensityofN20molecules
exitedbythephotolysislaserlight･ThefbrmationyieldofN(4s)atoms,◎N,丘omthe
photolysISOfN20at193nmisexpressedasfo1lows‥
◎N=
(Aph/AMW)ト]MW
×匙
GN2｡P20]I｡.,F;h
AphandAMWaretheareasoftheresonanCePeaksofthefluorescenceexcitationspectra
ofN(4s)atomsproducedinthephotolysisofN20at193nmandintheMWdischarge
ofN2,reSPeCtively,undersameconditionsfortheNatomdetection･P]MWisthe
concentrationofNatomproducedintheMWdischargeofN2,Whichcalibratedbythe
titrationtechnique･GN20isthephotoabsorptioncrosssectionofN20at193nm,8･95×
10.20cm2molecule.1【7].P20]istheconcentrationofN20inthechamber･hI,isthe
photondensityoftheincidentphotolysislaserlight,Whichwasmeasuredtobe8･4×
1016photonscm-2.Intensityvariationofthephotolysislaserlightwassma11(<5%)
throughoutthe
arethe
measurements･栴一andFhw
detection
efncienciesofthe
fluorescencemonitorlnginthephotolysisandMWdischargeexperiments,reSPeCtively,
wheretheexcitationvolumebytheprobelaserinthechamber,theoverlapreglOnOfthe
42
193nmphotolysISlaserwiththeprobelaser,andthesolidanglefromtheemitting
reglOnOntOthephotocathodeofthePMTaretakeintoaccount･ThelengtllOfthe
volumeexcitedbytheprobelaserintheviewlngZOneOfthePMTwas15mm,While
thatofthevolumewheretheprobelaserbeamoverlappedwiththephotolysislaserwas
6mm.Therefore,thevalueofF(MW)/F(ph)wasestimatedtobe2･5･Threesetsof
experimentswereperformedforthechemicaltitrationmethod･Consequently,￠NWaS
determinedtobe(2.25±0･71)×10-3･ThequotederrorincludesthelG-Statisticaland
estimated
systematic
uncertaintiesfor
the
VUV-LIF
detection
and
N
the
atom
concentrationcalibration.
3.3.2Photolyticcalibrationmethod
Figure3.4showsthefluorescenceexcitationspectrumforCl(2pl/2)atoms
producedinthe193nmphotolysISOfHCl･Bycomparlngtherelativeintensitiesof
LIFsignalsofN(4s)fromN20andCl(2pl/2)fromHCIphotolysis,theN(4s)quantum
yieldcanbeestimated･Experimentally,meaSurementSOfspectraforNandClatom
werealternativelyperformedbychanglngboththereactantsandlaserwavelengths･
ThequantumyieldforN(4s)fbrmation,◎N,丘omthephotolysisofN20at193
nmisobtainedbythefbllowlngequation:
&立地辿ら他◎｡1
◎N=AcIINON20[N20]fN?N
(3.5)
ANandAclaretheareasofresonancepeaksinthefluorescenceexcitationspectraof
N(4s)atomsinthephotolysisofN20andCl(2pl/2)atomsinthephotolysisofHCl,
respectively･1handlclaretherelativeprobelaserintensitiesforNandClatom
detectionwhichobtainedasaphotoionizationcurrentfromtheNOcontainingce11･
ThephotoionizationefncienciesofNOmoleculeusedat120･07and120･14nmarealso
takenintoaccount[9,10].GHClisthephotoabsorptioncrosssectionofHClat193nm,
8.69×10-20cm2molecule.1[7].【HCl]istheconcentrationofHClmoleculesinthe
chamber.fhandftlaretheosci11atorstrengthvaluesfortheN(2p23s4pl′2←2p34s3佗)
andCl(3p44s2D,/2←3p52pl′2)opticalexcitation･Thevaluesoffhand丘1aretaken
fr｡mthedatabaseofNdtiona11hstituteQ[StanLk7rdand乃chnologyPIST)[11]･q)N
andq)clindicatethedetectionefncienciesoftheresonancenuorescencefbrNandCl
atoms,reSPeCtively･AsforCl(2pl/2)atomdetection,theexitedCl(2D3/2)state
43
fluorescesat120.14andl18.88nm,Whichareresonanttothe2D3r2→2pl/2and2D3r2→
2p3/2tranSition,reSPeCtively･ThedetectionefncienciesofthePMTsystemamongthe
wavelengthsat120･07,120･14andl18･88nmfbrtheN(4pln→4s3/2),Cl(2D3/2→2p)n)
andC](2D3/2→2p,/2)emissionlines,reSPeCtively,areaSSumedtobeconstantsince
thosewavelengthareveryclosetoeachother･ThequantumyieldofCl(2pl′2)atomsin
thephotolysisofHClat193nmphotolysis,◎cI,isreportedtobeO･408[6]･Inthis
experiment,thecollisionalrelaxationandthechemicalreactionofCl(2pl′2)couldbe
lgnOred･ThepressuresofHClandArbufftrgaswere20and160mTorrandthetime
delaybetweenthephotolysISandprobelaserpulseswas130ns,andtherelaxationrate
ofCl(2pl/2)bycollisionwithHClandArare7･8×10-12and≦1･0×10-14cm3molecule･1
sets
s.1,reSPeCtively[12,13]Twenty-three
ofexperiments
were
performed
fbr
photolyticcalibrationmethod･Consequently,◎N=(1･70±1･21)×10-3wasobtained･
ThequotederrorincludesthelG-Statisticalandestimatedsystematicuncertainties･
The
the
results obtainedfrom
two
dif托rent experiments
ofthe
chemical
titrationandphotolyticcalibrationmethodsareingoodagreementwitheachother
withintheexperimentaluncertainties･ThequantumyieldvalueforN(4s)formationin
the193rmphotolysisofN20isdeterminedtobe(pN=(2･1±0･9)×10-3bycombining
thetwoexperimentsresultsformtwomethods,inwhichthem年一Orityoftheerror丘om
eachofthetwomethodsaresystematicuncertainties･
3.4Discussion
3.4.1DissociationprocessofN20toproduceN(4s)+NO
InthephotolysisofN20around200nm,therearefourenergeticallyavailable
dissociationpathways:
N20+hu
→
N2(Xl∑+g)+0(1D)
(3･1a)
→
N(4s)+NO(Ⅹ2口)
(3･1b)
→
N2(Ⅹl=+g)+0(3p)
(3･1c)
→
N2(Ⅹl∑+g)+0(1s).
(3･1d)
Inthisw｡rk,WedeterminedthequantumyieldforN(4s)productioninthephotolysisof
N20at193nm.Ourresultof◎N=(2･1±0･9)×10-3issmallerthantheupper-1imit
value
presented
by
Greenblatt
and
Ravishankara[3]･They
estimated
the
productionyield(Channe13･1b)byobservingthechemiluminescenceofNO2thatwas
formedbythereactionofO3andNOfragmentsproduced丘omN20photolysis･A
44
NO
quitesma11quantumyieldvaluecanbeexplainedbyaspin-fbrbiddennaturefbrchannel
(3.1b).
Figure3･5showsthecorrelationdiagramfbrthereactionsofO+N2andNO+
N,inwhichCssymmetryisassumedfbrthereactionintermediate[14]･N20has16
valenceelectronsandbelongstoCのVSymmetrygrOuPWhenitisinitselectronicground
statexl∑+(4G25G26G217t47G227t4configuration)･Thelowestelectronica11yexited
slngletstatesaretheAl=-,theBl△,andtheClrIstates･UponbendingtheCs
symmetrygroupappliesgivingrisetothellA′(】=+)andthellA′･(1=
)states･The口
and△statessplitintoA,andA,lcomponents･ThetheoreticalcalculationsbyHopper
showthatdissociationaround200nmoccursviathe21A･state,andthatthenearbyl
lA,･statecanalsobeinvoIvedinthedissociationprocess･Whilethe21A･stateispart
ofaRenner-Tellerpalr,thecomponentofthispairhasalinearequilibriumgeometry
anditsenergyincreasesrapidlyasthemoleculebends･Teuleetal･[15]studiedthe
photodissociationofN20around203nmbyatechniqueofphotofragmentimaglng,and
showedthatthepara11eltransitiontothe21A,stateisdominant･
Previous
studies
showedthatchannel(3.1a)is
dominantwithalmostunity
quantumyieldinthe193n皿PhotolysisofN20[1],Whichisrationalizedbythefact
thatboththe2)A,andllA･′statesadiabaticallycorrelatetothephotoproductsofO(1D)
+N2(Channe13･1a)･Inthepresentstudy,theN(4s)atomformation(Channe13･1b)is
observeddirectlybytheVUV-LIFmethodandthequantumyieldisdeterminedtobe
(2.1±0.9)×10-3.TheadiabaticcorrelationdiagramshowninFig･3･5suggeststhat
theintersystemcrosslngfromtheexitedsingletstatetothetripletstateordirect
photoexcitationtothetripletstatescanaccountfortheN(4s)formation･Aweak
spln-Orbitinteractionbetweentheslngletandtripletexcitedstatesorasma11tranSition
probability丘omthegroundtothetripletstatesmayresultsintheverysmallquantum
yieldfbrN(4s)fbrmationinN20photolysisat193nm･
3.4.2Atmosphericimplications
We
haveinvestigatedthe
atmosphericimportanceofchannel(3･1b)･The
stratosphericsinkofN20ismainlyduetoUVphotolysISintheatmosphericwindow
region.TheremainingsinkofN20isreactionwithO(1D)whichisproducedbythe
OZOnePhotolysIS:
N20+0(1D)→2NO
k3.2a=6･7×10-11cm3molecule-1s-1(3･2a)
45
k3.2b=4.9×10-11cm3molecule-Js
→N2+02
).(3.2b)
About60%oftheN20+0(】D)reactionproceedsviareaction(3･2a)andabout40%via
reaction(3.2b).Reaction(3.2a)isanimportantsourceofstratosphericNO･The
photolysisofN20proceedingsviaphotodissociationchannelN(4s)+NOcanalso
PrOVideastratosphericNOsource･
ThecurrentNASA/JPLevaluationsforstratosphericmodelingrecommendthat
thequantum
yieldforphotodissociationofN20around200nmisunity,andthe
productsareN2andO(lD)(channe13･1a),inspiteofreferringthattheyieldofN(4s)
andNO(2rI)islessthanl%･However,theN(4s)andNO(2rI)formation(Chame1
3.1b)canbeanon-negligibledirect軍OurCeOfstratosphericNOx･ThestratosphericO3
abundanCeanditsverticalpro丘1eareslgni丘cantlyafftctedbyNOx,becauseNOxcan
catalytically destroy
stratospheric
O3･In
this study,We
Ofchannel(3･1b)in
atmospherici甲POrtanCe
haveinvestigated
the photolysis
the
using
ofN20,by
one-dimensionaldynamical-Photochemicalmodel･Allchemicalschemesofthemodel
arethesamewiththatintheGarcia-Solomontwo-dimensional(GS-2D)model[16,17].
The
were
modelcalculations
performedincluding40chemicalspeciesand120
chemicalreactionswiththechemicalkineticsandphotochemicaldatapresentedbythe
recentJPLrecommendations[7].Weincludedchannel(3･1b)quantumyieldvalueof
2.1×10-3inthemodelontheassumptlOnthatitisindependentofthetemperatureand
wavelengthattheatmosphericwindowreg10n･
Figure3･6shows
the result
ofthe
photochemicalmodelcalculationsfor
latitudeof40degreeinMarch,Whichindicatesthechangeinthediurnallyaveraged
concentrationsofNOx,HOx,ClOxandO3COnCentrationscalculatedwithorwithout
chaJmel(3.1b)in
the
photolysis
ofN20･The
steady-State
NOx
concentration
calculatedbythemodelincludingcharmel(3･1b)increasesupto∼3%around25kmin
comparisonwiththatignoringchannel(3･1b),WhiletheHOxandClOxabundances
decrease.Thealtitude-dependentchangeintheNOxconcentrationshouldreflectthe
altitude-dependent
solarflux
attheatmosphericwindowwavelengthreg10n･The
concentrationsofHOxandC10xmaybeattributabletothefo1lowlngreaCtions‥
OH+NO2+M→HNO3+M
(3.6)
ClO+NO2+M→ClONO2+M
(3.7)
OH+HCl→Cl+H20.
(3.8)
TheconcentrationchangesofHOxandClOxarelargerinthelowerstratosphereas
46
a
showninFig.3･6,becausethecontributionofthree-bodyreactions(3･6)and(3･7)
becomesrnOreSignincantatlowerstratosphericaltitudes･Reaction(3･8)convertsthe
chlorinereservoirHClintoactiveClOx･ThedecreaseoftheHOxconcentrationmay
resultinthedecreaseofC10xthroughreaction(3.8).ThechemicalreactionsofNOx,
HOxandClOxfamiliesplayacrucialroleindeterminlngthestratosphericO3abundanCe,
andthustheconcentrationchangesofthesespeciesalterO3abundance･Inclusionof
channel(3.1b)inthemodelafftctstheproductionrateofNOx,Whichisfbllowedbythe
decreaseofO3abundancethroughtheenl1anCementOftheNOxcatalyzedO3destruction
rate,aSShowninFig.3･6･
47
1
(slモコ.qJe)倉su望u〓賢愚s山コ
0
-1
△v(Cm
1)
Figure3.1.FluorescenceexcitationspectraofN(4s)producedfromthephotolysisof
N20at19311m･The
horizontalscaleindicates
the wavenumber
resonanCelinecenterofthe4pl/2←4s3/2tranSitionforNatomat120･07nm･The
delaytlmebetweenthephotolysISandprobelaserpulseswas130ns･Thepressureof
N20was700mTorr.
48
shi氏丘om
the
(s}モ⊃･q立身su茎=空芳(s寸)Z
1
0
PhotolysisLaserPower(arb･units)
Figure3.2.LIFsignalintensityforN(4s)versusthephotolysislaserpower･The
photolysislaserpowerwaschangedwhilemonitoringtheN(4s)LIFsignalat12q･07
nm.Thetimedelaybetweenthephotolysisandprobelaserpulseswas150nsandthe
pressureofN20inthereactionce11was800mTorr･Solidlineistheresultsoflinear
weighted丘tanalysISOftheexperimentaldata･
49
(s}モ⊃･q立合su茎=eu君(s寸)Z
Figure3･3･PlotsofthetitrationfortheNatomsproducedbythemicrowavedischarge
ofN2.ThehorizontalaxisistheNOconcentrationaddeddownStreamOfthedischarge･
TheverticalaxisistheLIFintensityofN(4s).Thesolidlineindicatestheresultsof
thelst-Orderleastsquare丘tting･
50
1
(s}モコ･qJe)倉su盟u〓芦屋s]コ
0
0.5
ー0.5
△v(Cm
1)
Figure3･4･FluorescenceexcitationspectrumofCl(2pl/2)atomsproduced丘omthe
193nmphotolysisofHCl･Thehorizontalscaleindicatesthewavenumbershiftfrom
theresonancelinecenterofthe2D3/2←2pl/2tranSitionforClatomat120･07nm･The
delaytimebetweenthephotolysisandprobelaserpulseswas130ns･Thepartial
pressureofHCIwas50mTorr･
51
8
>む､誌｣2山uO焉}.5×山
2n
2D
2口
4s
11A′ン1･･
/21A′..･･
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●
●
●
●
●
1∑;3町
●■
N2
0
Xl∑+(11A′)
0
N20
Figure3.5.AnadiabaticcorrelationdiagramforN20P-NO,N20,N2-0)system
assumingaCssymmetry,WhichistakenfromHopper[14]･Theenergylevelsare
drawntOSCale.
52
N
(∈呈むP⊃茎<
ー3
-2
0
-1
1
2
ChangeinConcentration(%)
Figure3･6･CalculatedpercentagechangeSinNOx,HOx,ClOx,andO3COnCentrations
withtheN(4s)+NOdissociationchannel&omthosecalculatedwithouttheN(4s)+NO
channelforlatitudeof400ihMarChasafunctionofaltitude.
53
3
RcfbrcncesfbrChapter3
[1]Okabe,H.,Photochemist7yQrSmall肋Iecules,Jol-nWi)ey&Sons,NewYork,1978･
[2]Felder,P.,Haas,B.-M･,Huber,J･R･,Chem･P7p･Lelt･,186,177(1991)･
[3]Greenblatt,G.D.,Ravishankara,A･R･,JGeqpj叩･Res･,95,3539(1990)･
[4]Adams,S.F.,DeJosephJr･C･A･,Carter,C･C･,Miller,T･A･,Williamson,J･M･,JPjDLS･
C力e肌,AlO5,5977(2001).
[5]Zhang,J.,Dulligall,M･,Witting,C･,JChem･PjDLS･,107,1403(1994)･
[6]Boisse-Laporte,C.,Chave-Normand,C･,Marec,J･,PlasmaSourcesSti･乃chnol･,6,70
(1997).
[7]Sal-del･,S.P.,Friedl,R.R･,Golden,D･M･,Kurylo,M･J･,Huie,R･E･,Orkin,V･L･,
Moortgat,G･K･,Ravishankara,A･R･,Kolb,C･E･,Molina,M･J･,Finlayson-Pitts,B･J･,
ChemicalKineticsandPho10ChemicalDalajbruseinAlmo?PhericStudies,Evaluation
No.14,JPLPublicatiollO2-25,2003･
【8]Wennberg,P.0.,Anderson,J･G･,Weisenstein,D･K･,JGeqp7ws･Res･,99,18,839(1994)･
【9]Ono,Y.,Li1一,S.H.,Prest,tl･F･,Ng,C･Y･,JChem･P砂∫･,73,4855(1980)･
[10]El･man,P.,Karawqiczyk,A･,Rachlew-Ka)11-e,E･,Str6mholm,C･,JChem･P7p･,102,
3064(1995)
【11]Ma11in,W.C.,etal.,mSTAtomic勘ectraDatabaseh,erSion2･Q),NationalInstituteof
StandardsandTechnology,Gaithersburg,MD(http://physics･nist･gOV/asd),1999･
[12]Sotllichenko,S.A.,Bokun,V･Ch･,Nadkhin,A･I･,Chem･PJp･Lett･,153,560(1988)･
[13]Hitstlda,K.,Takahashi,K･,Matsumi,Y･,Wallington,T･J･,JP7vLS･Chem･,AlO5,5131
(200り.
[14]Hopper,D.G.,JChem･P7p･,80,4290(1984)･
[15]Teule,J.M.,Groel-enboom,G･C･,Neyer,D･W･,Chandler,D･W･,Janssen,M･H･M･,
C加憫｣甥叩.エe比,320,177(2000)･
[16]Solomon,S･,R･Portmann,W･,Garcia,R･R･,Tl-OmaSOn,L･W･,Poole,L･R･,McCormick,
M.P.,JGe呼砂∫.月e∫.,101,6713(1996)･
【17]Taniguchi,N.,Hayashida,S･,Takahashi,K･,Matsumi,Y･,Atoms･Chem･P7叩･,3,1293
(2003).
54
Chapter4
KineticsoftheatmosphericreactionsofN(4s)atoms
WithNOandNO2
4.1Introduction
PhotochemicalprocessesinvoIvingtheN(4s)atomandNOxmoleculesplaya
crucialruleintheterrestrialandplanetaryatmOSPheres[1,2,3,4]･Forinstance,the
reactionofN(4s)withnitricoxide:
(4･1)
N(4s)+NO→N2+0(3p),
hasbeenthoughttoactasasinkofoddnitrogeninthemiddleandupperterrestrial
atmosphere[1,2].Possible
signi丘cance
ofthe
reaction(4･1)in
Martian
the
and
VenusianatmOSPherehasalsobeensuggested[2]･ThereactionofN(4s)withnitrogen
dioxide:
(4･2)
N(4s)+NO2→N20+0(3p),
playsalessslgni丘cantroleasasinkofoddnitrogeninthemiddleterrestrialatmosphere
becauseofthesmallconcentrationofNO2[5].AsmallamOuntOfN20maybeformed
byreaction(4.2)intheMartianatmOSPhere[4]･FortheN+NO2reaCtion,Other
channelsfbrmlng2NO,N2+02,andN2+0+0,areenergeticallypossible･However,
thosechannelsaresuggestedtobeofminorimportanceasrelatedtoproducts[5]･
Althoughanumberofkineticstudiesofthereactions(4･1)and(4･2)havebeen
reportedatroomtemperature,aSlistedinTable4･1,agreementamOngthemisrelatively
poor･Inpreviouskineticstudies,SeVeralteclmiquessuchasmicrowavedischargeof
N2[5,6,7,8,9,10,11,12,13,14],VUVflashphotolysis
ofN20[10,15],andpulsed
radiolysisofN2[16],WereemPloyedtogeneratetheN(4s)atoms･ForN(4s)detection,
mass
spectrometry
techniques
were
usedin
severalstudies[6,7,8,9,13,14]･With
nitrogenatomlamps,reSOnanCenuOreSCenCedetection[5,10,11,12,15]andresonanCe
absorptiondetection[16]oftheN(4s)atomswerealsoused･Inthepresentstudy,itis
demonstratedthatthelasernashphotolysisNUV-LIFdetectionteclmiqueisapowerfu1
toolforthestudyofthekineticsofthereactions(4･1)and(4･2),inwhichtheN(4s)
formationfollowlng19311mArFlaserirradiationofNOandNO2hasbeenutilizedasa
photolyticsourceofN(4s)atoms.
55
TheN(4s)fbrmationfbllowing193nmArFlaserirradiationofNOunder
shock-heated
by
reported
conditions(1400-3500K)was
severalgroups[17,18],in
whichtheN(4s)atomsweremonitoredbyatomicresonanceabsorptionspectroscopyat
l19.9nm:
(4.3)
NO+hv(193nm)→N(4s)+0(3p).
Threed｡｡bletstatesofNOA2∑+(v･=3),B2n(v,=7),andC2rl(vl=3)1ienearthe
dissociationlimitofNO,aSShowninFigure4.1.TheysuggestedthatNatomsare
producedbydirectexcitationofvibrationallyexcitedstatesofNO(X2n,V≧1)tothe
D2∑+state,fbllowlngCOnVerSionfromtheD2=+statetothepredissociatingC2rIstate･
Inthepresentstudy,thenrstobservationoftheN(4s)formationfo1lowing193nm
irradiationofNOat295Khasbeenreported･PhotoexcitationprocessesofNOgiving
risetotheN(4s)atomformationat295Khavebeendiscussed･
Photoexcitation
processes
the
ofNO2in
UV
reglOnhave
beenthoroughly
investigatedatよnumberofwavelengthsotherthan193nm[19]･At193nm,thereare
onlyalimitednumberofexperimentalstudiesonthephotoexcitationprocesses･The
fo1lowlngtWOChannelsarethoughttobedominantasphotodissociationpathwaysat
193nm,
(4.4a)
NO2+hv(193nm)→NO(X2n)+0(3p)
(4.4b)
→NO(Ⅹ2口)+0(lD),
and
the
branching
ratiofor
O(1D)and
O(3p)productions
was
estimated
be
to
[0(1D)]/([0(lD)]+[0(3p)])=0.55±0･03[20]･GraddandSlanger[21]observedthe
vibrationallyexcitedNO(X2n,V=4-10)inthephotodissociationofNO2at193nm･
Gongetal.[22]reportedthatthenascentvibrationalstatepopulationsofNO(X2Il,
v=1-7)inthephotodissociationofNO2at193nmhaveamaximumatv=5･Tsqjiet
al.[23]studiedthedecompositionofNO2inN2atmOSPhereat193nmbyArFlaser
irradiation,and
observed
alowerNO
yield than
that predictedfrom
simple
NO2
photolysis(reactions4･4aand4･4b)atalowNO2COnCentrationof200ppm･They
suggestedthatthelowerNOyieldwasattributabletothephotolyticlossofvibrationally
excitedNOwhichwasprimarilyproduced丘omNO2Photolysisat193nm･TheN(4s)
andO2PrOductionsareenergeticallypossibleintheUVreglOnbelow272nm‥
(4.4c)
NO2+hv→N(4s)+02.
Matsumietal.[24]detectedlaser-inducednuorescencefromthevibrationally
excitedO2mOleculesaround220-300runfo1lowlngtheirradiationoffocusedvisible
56
1aserlight(470-580nm)onNO2gaS,andsuggestedthatthevibrationallyexcitedO2
were
molecules
directly
producedfrom
a
multiphoton
absorptlOn
PrOCeSS
OfNO2.
However,furtherexperimentalstudiesrevealedthattheO2mOleculeswereproduced
from
the
reaction
of
O*+NO2Where
O*was
generatedfrom
the
multiphoton
dissociationofNO2[25,26].Therehasbeennoexperimentalobservationofchannel
(4.4c)withtheirradiationofArFlaser.Inthepresentstudy,the丘rstexperimental
observationoftheN(4s)production丘omNO2Withhigh-POWerArFlaserirradiationat
193nmhasbeenreported.ThephotoexcitationprocessesofNO2glVlngrisetothe
N(4s)fbrmationhavebeendiscussed.
4･2Experimental
ThedetailsoftheapparatususedinthepresentstudyareShowninChapter2
andhereonlyadescriptionrelatedtothischapterwi11begiven.NOgas(>99%,Nihon
Sanso)purchasedwasusedaRerpuri丘cationbypassingitthroughacoldtrapthatwas
immersedinamethan01/1iquidN2Slushbathat175K.Heliumgas(>99.99%,Iwatani
Gas)wasusedwithoutfurtherpuri丘cationinthekineticexperiments.Muchattention
WaSPaidtothehandlingofNO2gaSreagentinthisstudy,Sincepuri丘edNO2gaSiseasy
todegradetoNOmixtureandthereactionrateconstantofNOwithN(4s)hasbeen
reportedtobeabout5timeslargerthanthatofNO2(Table4.1).TheNO2gaSWaS
Synthesizedbymixingthepuri丘edNOgaswithexcessO2(>99.99%,NihonSanSO)ina
glassvessel(2L),andstoredinthevesselformorethanseveraldayspriortouseinthe
experiments.ThetotalpressureoftheNO2/02VeSSelwasabout700Torrwiththe
mixingratio[NO2]:[02]彩1:3.FortheNO2Photolysisandkineticsexperiments,the
gasmixtureofNO2/02WaSSuPPliedtothereactioncelldirectlyfromthevesselthrough
amassflowcontroller.N204equilibrateswithNO2gaS.Theequilibriumbetween
NO2andN204inthereactantgaSWhichwasnowedintothereactioncellwasestimated
tobeattainedwithinlO
6s[19]beforethelaserirradiation.Whenthepartialpressure
ofNO2islxlO16moleculecm-3,thepartialpressureofN204isaboutl/4000fNO2at
298kusingtheequilibriumconstantPreSentedbyNASA/JPL[27].
TheconcentrationofNO2inthereactionchamberwasdetermineddirectlyby
absorptlOn
meaSurementS･The
collimated
output
ofa
tungstenlamp
was
throughthereactionchamberandfbcusedontotheentranceslitofaspectrographwitha
2048-elementdiodearraydetector(OceansOptics,HR2000,f=101mm).AlO-Llm
57
passed
entranceslitwasusedfbrabsorptionmeasurementsataresolutionof∼0･7nm･The
absorptlOnfbaturesoftheNO2SPeCtrumreCOrdedbetween300and650nmareingood
agreement
with
previous
wavelength
measurements[28,29,30]･The
the
of
spectrometerwascalibratedat404･66and435･84nmuslnganHgpenraylamP･The
concentratiollOfNO2WaSdetern1inedbyabsorpt10nmeaSurementSarOund413･7nmon
thebasisofthereportedabsorptiohcross-S占ction[28,29,30].ThecontributionofN204,
ifpresent,isminirrlizedatthiswavelength,aSdescribedbyGierczaketal･【30]･The
uncertaintyassociatedwiththemeasurementsofNO2COnCentrationwasestimatedtobe
∼10%.Allexperimentswereperformedat295±2K･
4.3.Resultsanddiscussion
4.3.1N(4s)productionfbllowing193nmlaserirradiationofNO
Figure4･2ashows
atypICalnuorescenceexcitationspectrumofthenascent
N(4s)atomsproducedfo1lowing1931皿1aserirradiationofNO,Whichwasobtainedby
scannlngtheprobelaserwavelengthacrossthe2p23s4pl/2-2p34s3r2tranSitionat120･07
nm･Thespectrumwastakenat80nsdelaytimewith145mTorrofNO,andnobu脆r
gaswasadded･Itshouldbenotedthatthedissociationlimitofrovibrationallycold
NOgivingrisetotheN(4s)+0(3p)channelis52397土2cm.1[31],Whichisslightly
largerthanthephotonenergyoftheArFlaserradiation(193.3nm)of51730cm.l.To
revealthephotodissociationprocessesofNOproducingtheN(4s)atom,Photolysislaser
LIFsignalwasmeasured･AsshowninFigure4･3a,We
powerdependenceofthe
found
thatthe
LIFintenslty
dependent
WaSlinearly
onthe
photolysislaserpower･
WhenweturnedtheArFexcimerlaseroff;noobviousLIFsignalwasobserved.This
indicatesthattheN(4s)productionfromtheNOphotodissociationat120nmwas
negligibleunderourexperimentalconditions･TheseresultssuggestthattheN(4s)
fbrmationobservedinthisstudywasattributabletotheone-Photonexcitationprocessof
NO:
(4.3)
NO+hv(193nm)→NぐS)+0(3p).
Tochecktheinterftrenceinthemeasurementsbecauseofimpurities,WereCOrdedthe
nuorescenceexcitationspectraofthenascentN(4s)atomsproducedfrompuri丘edand
nonpuri丘edNO･No
slgni丘cantchangeWaS
Observedinthe
slgnalintensitiesand
spectralshapesofN(4s).
ThreedoubletstatesofNOA2∑+(v=3),B2Il(V=7),andC2口(V=3)1ienear
58
thedissociationlimitofNO･DavidsonandHanSOn[17]andKoshietal.[18]reported
theN(4s)fbrmationfb)lowing193nmlaserirradiationofNOundertheshock-heated
N(4s)atomformation
conditions.The
vibrationally
excited
states
was
attributed
X2口(v≧1)tothe
ofNO
to
direct
excitation
D2∑+state[17].In
of
our
experimentswhichwereperformedatroomtemperature,itisun1ikelythatthedirect
photoexcitationfromtheNOX2n(v=1)totheD2∑+(V=0)stateissignificantly
responsibleforN(4s)fbrmation,becausethepopulationofvibrationa11yexcitedNO
X2rI(v=1)isnegligiblysmallatroomtemperature.
ShibuyaandStuhl[32,33,34]investigatedtheexcited-StateSdynamicsofNO
throughthemeasurementsofemissionspectraandfluorescencelifetimesfo1lowlng193
nmlaserirradiation.TheyobservedthenuorescencefromB2H(V=7),C2n(V=0),
andA2∑(v=3)states.The193-nmlaserlightcanberesonantWiththeabsorptionof
theNOB2n(v=7)←X2口(v=0)andA2∑(V=3)←X2口(v=0)tranSitions.Fromthe
availablespectroscopicdata【35],NOX2rI(V=0)isexpectedtobeexcitedtothe
B2n(v=7)stateviatheabsorptionlinesR11(30.5-32.5),Pl.(27.5-29.5),Qll(28.5-31.5),
R22(28.5-30.5),P22(25.5-27.5)andQ22(26.5-29.5).TheA2∑(v=3)statecanalsobe
preparedviatheabsorptionofX2Il(v=0,J∼50.5).TheBoltzmannpopulationofthe
X2口(V=0,J∼50.5)stateismuchsmallerthanthatofX2Il(V=0,J∼28.5)at295K.
ShibuyaandStuhl[32,33,34]suggestedthattherotationallevelsofJ=21.5-34.5forthe
F)COmPOnentandJ=20.5-33.5forthe為componentoftheB2口(V=7)statewere
preparedfo1lowing193nmexcitationatroomtemperature,andthattheC2n(v=0),and
A2∑(v=3)stateswereproducedbythecollisionalrelaxation丘omtheB2口(v=7)state.
They
alsoindicated
that
the
phot?eXCitedlevels
of､the
B2口(v=7)stateare
predissociativeandthatthenuorescencequantumyieldisaboutO･15and<6×10-3for
J=20.5-29.5andJ>29.5,reSPeCtively.Therefore,itislikelythattheN(4s)atom
formationobservedinthe193nmlaserirradiationofNOinthisstudyisduetothe
photoexcitationtothehighrotationallevelsoftheB2n(V=7)state,Whichisfo1lowed
bythepredissociationtoN(4s)+0(3p).
TheDopplerpromeofthenascentN(4s)atomsproducedfromthe193nm
irradiationofNO(Fig.4.2a)isslightlywiderthanthatofthethermalizedN(4s)atoms
(brokencurveinFig･4･2b).Thekineticenergyreleaseinchannel(3)isestimatedto
be∼1000cm.1fromtheDopplerpro創eofthenascentN(4s)atoms.Thisisconsistent
Withthefactthatthehighrotationa11evels(FIJ=2l.5-34.5,F2J=20.5-33.5)inthe
59
B2n(v=7)statelieabovethedissociationlimitby500-1100cm.l.
4.3.2
N(4s)productionfbIlowing193nmlaserirradiationofNO2
Figure4.2bshowsatypicalexamPleofthenuorescenceexcitationspectrumOf
thenascentN(4s)atomsproducedfromthe193nmlaserirradiationofNO2,inwhich
gaspressureinthechamberwas34mTorrand82mTorrforNO2andO2,reSPeCtively,
Withoutbuffbrgas.Thespectrumwastakenat80nsdelaytime.TheFWHMofthe
spectrumwasestimatedtobel.38cm.1withaGaussianshape(Fig.4.2b).Assuming
theMaxwell-BoltzmannVelocitydistribution,the
averagetranSlationalenergyofthe
nascentN(4s)atomsinthelaboratory(LAB)&amewascalculatedtobe∼7500cm.1
(∼21kcalmol
1).
Figure4.3b
shows
a
photolysislaser
power
dependence
ofthe
LIF
signal
intensityofN(4s)atomsproducedfromthe193nmlaserirradiationofNO2.A
quadraticphotolysislaserpowerdependenceoftheN(4s)LIFsignalintensitysuggests
thattheN(4s)formationisattributabletothesequentialtwo-Photondissociationprocess
OrthesimultaneOuSabsorptionoftwophotonsbyNO2.
For
the
sequentialtwo-Photon
dissociation
that the
process,itislikely
vibrationallyexcitedNO(X2n,V)isproduced丘omthephotolysisofNO2at193nm,
andthenNO(X2口,V)isphotolyzedtoproducetheN(4s)atom:
NO2+hv(193nm)→NO(X2口,V)+0
(4.4)
NO(X2口,V)+hv(193nm)→N(4s)+0.
(4.5)
GraddandSlanger[36]observedthevibrationallyexcitedNOX2n(V=4-10)inthe
Photodissociation
et
ofNO2at193nm･Gong
al･【22]reported that the
nascent
vibrationalstatepopulationsofNOX2Il(v=1-7)inthephotodissociationofNO2at193
nmhaveamaximumatv=5.TheaveragetranslationalenergyofN(4s)estimatedin
thepresentstudy(∼21kcal/molinthelaboratoryframe)isconsistentwiththesequential
two-PhotondissociationprocessinwhichNO(X2口,V=7)isformedthroughcharmel
(4.4).
ForthesimultaneOuStWO-Photonabsorptionmechanism,itinvoIvesthedirect
formationofN(4s)fromanelectronica11yexcitedstate(S)ofNO2,Wherethefo1lowing
Channelsareavailablethermochemically:
NO2+2hv(193nm)→N(4s)+20
(4.6)
NO2+2hv(193nm)→NO*+0→N(4s)+0+0
(4.7)
60
(4.8)
NO2+2hv(193nm)→N(4s)+02.
HaakandStuhl[37]observedtheNOemissionsfromitsseveralexcitedstates(A2∑+,
D2∑+,andE2∑+,andsoon)fbllowingthemultiphotonabsorptionofNO2at193nm.
Further
studies
are
required
to
the
elucidate
mechanism
oftheN(4s)fbrmation
fbllowlng193nmirradiationofNO2･
4.3.3ReactionkineticsofN(4s)+NOandN(4s)+NO2
TheN(4s)fbrmationfo1lowing193nmirradiationofNOandNO2WaSaPPlied
tothekineticstudiesofthereactiong(4.1)and(4.2).ThepulsedArFlaserlightwas
usedtoirradiated150-570mTorrofNOinthepresenceofl.8TorrofHediluentand
thechemicallossofN(4s)wasmeasuredtodeterminetheratecoefncientsfortheN(4s)
+NOreactionat295±2K･Figure4･4showsatypICalexampleofthetemporal
pronleoftheN(4s)LIFintensityfbllowingpulsedArFlaserirradiationofamixtureof
415mTorrofNOandl.8TorrofHediluent,inwhichtheVUVlaserwavelengthwas
丘xedattheresonanCeCenterOftheN(2p23s4pl/2-2p34s3/2)transition(120.07nm).
Thetime-reSOIvedVUV-LIF…SignalofN(4s)atomsexhibitsaninitialjumpdueto
photolyticformationofN(4s),followedbyaslowdecayduetoitschemicalremovalin
c｡IlisionswithNOmolecules.ForthekineticstudyoftheN(4s)+NO2reaCtion,the
timepro創esoftheN(4s)LIFweremeasuredundertheconditionsofNO260-570
mTorr,02200-1700mTorr,andHe3･OTorr･Asdescribedintheprevioussection,the
translationallyhotN(4s)atomsareproducedfo1lowing193nmirradiationofNOand
NO2.ThetranslationallyhotN(4s)atomsarethermalizedwithin2psunderour
experimentalconditionsincollisionswithhelium,Whichwascon丘rmedbymeasurlng
theDopplerpro丘1esofN(4s)atoms･Thechemica1lossofN(4s)byreactionwithO2
cansafblybeignoredunderourexperimentalconditions([02]=200-1700mTorr,delay
timeO-20ps)becauseofitssma11rateconstantof8･5×10-17cm3molecule-1s-1at298K
[27].F｡rboththereactionsystems(4.1)and(4.2),Single-eXPOnentialdecaywa去
observedfortemporalpromesofN(4s)astypicallyshowninFig.4.4:
P(4s)]t=P(4s)]｡×eXP(-k,t).
Thepseudo-nrSt-Orderrateconstantk一foraparticularreaCtantPreSSureWaSderivedbya
nonlinearleast-SquareS丘tanalysIS･TheresultantdependencesofthekTvaluesonthe
n｡mberdensitiesofNOandNO2fortlleN(4s)+NOandN(4s)+NO2reaCtions,
respectively,areShowninFigure4･5･Linearleast-SquareSBtanalysISOfthedatain
61
(4･9)
Fig.4.5yieldedthebimolecularrateconstantSOfkNO=(3･8±0･2)×10-‖andkNO2=
(7.3±0.9)×10-12cm3molecule-1s-1at295±2K･Thequoteduncertaintiesoftherate
constantSinclude2GStatisticaluncertaintiesandestimatedsystematicerrors.
TherateconstantSfbrreactions(4.1)and(4.2)at295±2Kdeterminedinthe
presentstudyarelistedinTable4･1withavailableliteraturedata･ThekNOValue
determinedinthis
Wennberg
et
studylSinexce11entagreementwiththelatestdatareportedby
al.【5]within
the
quoted
uncertainties･Our
resultis
good
alsoin
agreementwiththatofCheahandClyne[11]andoneofthevaluesreportedbyLeeetal･
[10].ThelatestNASA/JPLrecommendedkNOValueat298K[27]issmallerthanboth
thevaluesrecentlyreportedbyWennbergetal･[5]andobtainedinthepresentstudy･
ForthereactionofN(4s)+NO,thegroundpotentialenergysurface(PES)3A′′andthe
nrstexcited
PES3A･weretheoretica11ylnVeStigatedby
meanS
Ofcomplete
active
spacesecond-Orderperturbation(CASPT2)method,andthevariationaltransitionstate
theoryprovidedthetemperature-dependentratecoefncients[38]･Itwasshownthat
the3A･PESwasmainlyresponsiblefortheN(4s)+NOreactionoverthetemperature
rangeOf200-5000KandtheirkNOValueat300Kwas4･68×10-11cm3molecule-1s-1･
ThetheoreticalvalueislargerthanOureXPerimentalandpreviousdeterminations･
ThekNO2ValuesreportedpreviouslyrangefromO･14to3･8×10-1)cm3
molecule-1s-1aslistedinTable4.1.ThekNO2Valuedeterminedinthisstudyislarger
thantheresultofClyneandOno[12],andissma11erthanthatpresentedbyWennberg
etal.[5].TheexperimentalteclmiqueoflaserflashphotolysiscombinedwithVUV
laser_inducedfluorescencedetectionhasbeenutilizedforthe丘rsttimeinthisstudy,
whileClyneandOno[12]andWennbergetal･[5]usedthetechniqueofdischargeflow
andresonancenuorescencedetectionwithanitrogenlamp.ClyneandMcDermid[9]
andClyneandOno[12]reportedthatthemeasuredrateconstantkNO2decreaseasthe
ratioof[NO2]/P(4s)]oincreaseatlowerratiosofPO2]/P(4s)]0(<80)･Theyargued
that
the
change
Ofthe
observed
rate
constant
WaS
due
to
catalyticinterftrences
invoIvingbothH(2s)+NO2andO(3p)+NO2reaCtions,inwhichH(2s)andO(3p)
atomscanbeproducedasimpuritiesinthemicrowavedischargeprocessandO(3p)
atomscanalsobeproducedthroughreaction(4･2)･Inthepresentstudy,N(4s)atoms
wereproducedfromthe193nmpulsedlaserirradiationofNO2,andtheratioof
PO2]/P(4s)]owas(5-20)×105asestimatedbyconsideringtheN(4s)detection
sensitivity(2×109atomscm-3).
62
Itshouldbenotedthat,1ngeneral,theliteraturedataoftheratecoefncientsfor
N(4s)reactionswith
simple
molecules
are
more
scattered
than
those
ofother
atmosphericreactionsinvoIvingatomssuchasO(lD)andCl(2n)atoms･Thismightbe
attributabletotherelativelylowreactivityofN(4s)towardthesimplemoleculesandthe
lackofapplicable
newly
experimentaltechnique･The
presented
teclmique
investigationoftheN(4s)reactionswithNOandNO2Willbeapplicabletoexamine
someotherN(4s)reactionsasafunctionoftemperatureandpressure･Thepulsedlaser
photolysis′VUV-LIFtechniquehasbeenutilizedasapowerfultooltostudythekinetics
anddynamicsofatmosphericreactionsinvoIvingO(1D)andCl(2pj)atoms[39,40]･
63
fbr
(T∈0寸○こ岳｣￠u￠一票uむlOd
4
1
lnternucleardistance(Å)
Figure4.1.PotentialenergycurvesofNOnearthedissociationlimitintotheN(4s)+
0(3p)products[41].
64
(.q立身su叫7ニ山コ(s寸)Z
0
Figure4.2.FluorescenceexcitationspectraofN(4s)producedfromthe193nmlaser
irradiationof(a)NOand(b)NO2,reSPeCtively,Whichwererecordedbyscanningthe
probelaserwavelengthacrosstheresonancecenterofthe4pl/2-4s3/2tranSitionfbrthe
N(4s)atomat120･07nm･ThesolidcurvesindicateGaussianShapesthat丘tthe
observedspectrum･Spectrum(a)wasmeasuredatan80nsdelaytimebetweenthe
photolysisandprobelaserpulsesatthepressureofNO145mTorr･Spectrum(b)was
measuredatan80nsdelaytimeatthepressuresofNO234mTorrandO282mTorr･
ThebrokencurveshowsthenuorescenceexcitationspectrumofthermalizedN(4s),in
whichtheN(4s)atomwasproduced丘om193nmirradiationofNO2inthepresenceof
3.6TorrofHe.ThedelaytlmeWaS5トLS･
65
(.q｣且倉su叫言二山コ(s寸)Z
10
1
PhotoIysislaserpower(arb,)
Figure4･3･PlotsofthephotolysislaserpowerdependenceoftheLIFintensityof
N(4s)producedfbllowing193nmlaserirradiationof(a)NOand(b)NO2,reSPeCtively･
ThephotolysislaserpowerwasvariedwhilemonitoringtheN(4s)LIFsignalat120･07
nm･Theprobelaserpowerwaskeptconstantduringthemeasurements･Solidlines
indicatetheresultsofleast-SquareS丘tanalysisinordertodeterminetheordernoflaser
powerdependenceoftheLIFsignals･Thevaluesobtainedfornare(a)0･9土0･1and
(b)1.7土0.2,reSPeCtively,Whicharedescribedinthe丘gure･Thequoteduncertainties
indicatethe2GerrOrSOfthe丘t.
66
(ム立身su茎こコ(s寸)Z
0
DeIaytime(10,6s)
Figure4･4･AtypicalexampleofthetemporaldecaycurveOfN(4s)LIFintensity
fbllowlngthe193-nmPulsedlaserirradiationofthegasmixturecontalnlng415mTorr
ofNOandl.8TorrofHediluentat295±2K･Thesolidcurveisa丘rst-Orderdecay
丘ttothedatainthetimedomainafter2ドS.
67
5
(TUむSの○こむl空よ村試占
0
2
【N00rN02](1016moleculescm
3)
Figure4.5.Plotofpseudo-nrSt-Orderdecayrates(k')versustheconcentrationofthe
reactants(a)NOand(b)NO2.Resultsoftheleast-SquareS丘tanalysisofthedataare
drawnbystraightlines,Whichyieldtheratecoefncients(3.8±0.2)×10.)1and(7.3±
0.9)×10.12cm3molecule-1s,1at295±2KforN(4s)reactionswithNOandNO2,
respectively.
68
Table4･1･Summaryofthepresentandpreviousstudiesonthereactionkineticsof
N(4s)withNOandNO2atrOOmtemPerature.
Reactant
Ratecoefficienta
Methode
Ref§.
1.7士0.8b
DF/MS
He汀On(1961)[6]
2.2士0.6
DF/MS
PhilipsandSchiff(1962)[7]
2.2土0.2
DF/MS
ClymeandMcDermid(1975)[9]
2.7土0.4C
DF/RF
Leeetal.(1978)[10]
4.0土0.2C
FP/RF
Leeetal.(1978)[10]
l.9土0.2
PR/RA
Sugawaraetal.(1980)[16]
3.4土0.3C
DF/RF
CheahandClyne(1980)[11]
4.5土0.2
FP/RF
HusainandSlater(1980)[15]
2.77土0.04C
DF/Rf
ClyneandOno(1982)[12]
2.03士0.17C
DF/MS
BrummingandClyne(1984)[13]
2.4土0.2
DF/MS
Jeoungetal.(1991)【14]
3.6士0.4d
DF/RF
Wennbergetal.(1994)[5]
NASA/JPL(2003)[27]
3.0
3.8士0.2d
LPNUV-LIF
Thiswork
1.85士0.22C
DF/MS
PhilipsandSchiff(1965)[8]
O.14士0.02
DF/MS
ClyneandMcDermid(1975)[9]
3.8士0.1
FP/RF
HusainandSlater(1980)[15]
0.301土0.033C
DF/Rf
ClyneandOno(1982)[12]
l.2士0.1d
DF/RF
Wennbergetal.(1994)[5]
NASA/JPL(2003)[27]
l.2
0.73土0.09d
LP/VUV-LIF
Thiswork
a.InunitsoflO-11cm3molecule-1s-1.
b.
Theerrorlimitsareestimatesof3G.
c.
TheerrorlimitsareestimatesoflG.
d.
Theerrorlimitsareestimatesof2G.
e･Experimentaltechniques･DF‥dischargenow,MS:maSSSPeCtrOmetry･KS:
kineticspectroscopy,RF:reSOnanCenuOreSCenCe,FP:naShphotolysIS,PR:Pulsed
radiolysIS,RA:reSOnanCe
absorption,LP:1aser
ultravioletlaser-inducednuorescence.
69
photolysis,VUV-LIF:VaCuum
RcfbrcncesfbrChapter4
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Chen,C.,JChem.P々叩.,93,8703(1990),
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Jenkin,M･E･,Rossi,M･J･,andTroe,J.,Atmos.Chem.P句岱.,4,1461(2004).
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71
Chapter5
TranslationalrelaxationofsuprathermalN(4s)atoms
intheupperatmosphere
5.1Introduction
Observations
ofNO
reevaluatetheproduction
densityln
processes
the
havelead
thermosphere
to
ofNOinthethermosphere,because
a
need
to
slgni丘cant
discrepanCybetweentheobservedabundanceandmodeledestimationfbrNOhasbeen
that
identi丘ed【1,2,3].In1983,Solomon[4]proposed
chemicalreaction
of
tranSlationallyhotN(4s)atomswith02mOleculescouldbeanewsourceoflower
thermosphericNO:
(5.1)
fastN(4s)+02→NO+0.
TheN(4s)+02reaCtionhasalargeactivationenergyof∼0.24eV(=5.5kcalmol-1)[5]
whichresultsinanegligiblysmallratecoefncientattypICaltemperaturesencountered
inthelowerthermosphere.ThesuprathermalN(4s)atomsproducedinthelower
thermospheremayreactwithO2tO
fbrmNO
atanenergydependentratewhichis
COnSiderablylagerthanthatatthermalequilibriumforambienttemperatures[e･g･4]･
Sincethen,mOdelcalculationshaveextensivelybeenperformedtoevaluatethe
tranSlationalenergydistributionsofN(4s)andtheformationefnciencyofNOthrough
reaction(5.1)undersuprathermalcollisionsinthethermosphere[4,5,6,7,8,9,10]･The
suprathermalnitrogenatomsinthethermospherecanbeproducedbyanumberof
processesincluding
dissociative
recombination
of
ofNO+,CO11isionalquenching
electronica11yexcitedN(2D)atomsandphotodissociationandphotoelectronimpact
dissociationofN2.Then,thosehotatomsarerelaxedbycollisionswithN2andO2
moleculesintheambientair.Inthemodelcalculationsofthesteady-StatetranSlational
energydistributionsofN(4s)atomsinthethermosphere[4,5,6,7,8,9,10,11,12,13,14],
thethermalizationratesinco11isionswithN2andO2mOleculesarecrucial.However,
nolaboratorystudydetermlnlngeXPerimentallythethermalizationcross
suprathermalN(4s)atomsincollisionswithambientgaseshasbeenreported.
fastN(4s)+N2→SlowN(4s)+N2
fastN(4s)+02→SlowN(4s)+02
72
sectionsof
Inthemodelcalculations,the
cross
N(4s)inN2[4,11,12,15]orthat
diffusionstudies
sectionthatestimated丘om
computedusing
classicaltr毎ectory(QCT)methods[8,9,13,14]have
quantum
of
meChanical(QM)and
been
utilized･Thelack
of
precisioninthethermalizationcrosssectionsresultsinaslgnincantuncertaintyinthe
modelcalculationsforthefbrmationrateofNOthroughreaction(5.1).
Inthepresent
collisional
study,thefirstexperimentaldeterminationofthe
relaxationratesofsuprathermalN(4s)inco11isionswithN2,02,HeandArhasbeen
reported.AsmallamOuntOfNO2dilutedinanexcessam0untOfbathgases(N2,02,
HeandAr)isphotolyzedat193mm,andthesuprathermalN(4s)atomsproducedare
detected
by
a
technique
of
VUV-LIF･Measurements
Doppler
time-reSOIved
of
pronlesofthesuprathermalN(4s)atomsenableustoevaluatethetime-dependent
tranSlationalenergy
experimentalresults
distributions
andMonte-Carlo
of
the
bath
N(4s)atomsin
calculations
based
gas.From
onanelastic
hard-SPhere
model,thecollisionradiibetweenN(4s)andthebathgasmoleculesaredetermined.
5･2Experimental
ThedetailsoftheqpparatuSuSedinthepresentstudyareshowninChapter2
andhereonlyadescriptionrelatedtothischapterwillbeglVen･A11theexperiments
wereperformedunderbulbconditionsat295±3K,inwhichgasmixturesofasma11
amountofNO2dilutedinbathgasP2,02,HeorAr)wereslowlyintroducedintoa
reactionchamber.ThetranslationallyhotN(4s)atomswereproducedby193nm
pulsedArFlaserphotolysisofNO2(SeeChapter4)･ThedensityofthehotN(4s)
atomsproducedbythelaserphotolysiswaslO9-1010atomscm-3,Whichwasmuch
smallerthanthatofbathgas(1016moleculescm-3).Thetimewidthsofthephotolysis
laserandprobelaserpulseswere∼15nsand∼10ns,reSPeCtively･Thedelaytime
betweenthephotolysIS
andprobelaserpulseswassetto30ns-5巨S,Whichwas
controlledbyadigitaldelaygenerator(StanfordResearch,DG535)･
5･3Experimentalresults
TheDopplerpro丘1esofN(4s)atomswererecordedbyscalmingtheprobelaser
wavelengthacrosstheresonanCeCenteratVariousdelaytimesbetweenthephotolysis
ArFlaserandprobeVUVlaserpulses･TheDopplerpronlesrenectthedistributionof
thevelocitycomponentofN(4s)atomsalongthepropagationdirectionoftheprobe
73
the
VUVlaser[16].We丘rstrecordedtheDopplerpro丘Iesat50nsdelaytimewithll
mTorrofNO2Withoutanybathgasundertwo
geometrica11aserbeamCOnditionsof
kp//Edandkp⊥Ed,WherekpandEdarethepropagationdirectionvectoroftheprobe
VUVlaser
and
the
polarization
vector
ofthe
photolysISlaser,reSPeCtively.The
promesprovidethenascenttranSlationalenergyofN(4s)producedfromNO2Photolysis,
becausetherelaxationisnegligibleunderthoseconditions.Wedidnotobserveany
difftrenceintheDopplerlineshapesbetweentwocon丘gurations,Whichindicatesthe
directionoftherecoilvelocitiesintheNO2PhotolysisisisotropIC.
Figure5.1showstypicalDopplerpromesofN(4s)atomsatvariousdelaytimes
ineachbathgasofN2andO2.TheDopplerwidthbecomesnarroweratlongerdelay
timesduetorelaxationofthefasttranSlationalspeedofN(4s)atomsbycollisionswith
thebu脆rgas,aSShowninFig.5.1.A氏erthedelaytimeoflトLS,nOSlgni丘cantchange
intheDopplerpro丘1eswasobserved.Thisindicatesthatthetranslationaldistribution
ofN(4s)wasentirelythermalizedtothatatambienttemperature(295K).TheVUV
laserlinewidthwasestimatedtobeO.40cm-1(FWHM)withaGaussianShqpefromthe
Dopplerpro丘1esofentirelythermalizedN(4s)atoms.Itwasfoundthatallthepronles
atanydelaytimeswerewe11reproducedbyGaussianShapes.AGaussianlineshape
COrreSPOnds
to
anisotropIC
Maxwellian
distribution
of
velocities.The
average
translationalenergyofN(4s)atomsintheLABname,<Et>,WaSCalculated丘omthe
GaussianDopplershape,uSingthefbllowingexpression[16]:
<Et>=忘(封mc2,
(5･2)
Where△vistheFWHMoftheGaussianShape丘ttedtotheDopplerpro丘1e,Vois■the
resonanCeCenterfrequency,misthemassofnitrogenatom,Cisthespeedoflight.
Theinitial<E.>Valueatt=OwasO.93±0.10eV(21.4±2.2kcalmol-1),Whichwas
calculatedfromtheN(4s)Dopplerpro丘1erecordedat50nsdelaytimewithoutbathgas.
Figure5.2ashowstheaveragetranslationalenergyofN(4s)atomsintheLAB
frame,<El>,aSafunctionofdelaytime,Whenthebathgaswasl.OTorrofO2.The
relativeconcentrationsofN(4s)asafunctionofdelaytimewerealsorevealedby
integratingthepeakareaofDopplerproⅢe.TheN(4s)concentrationateachdelay
timewasnormalizedwiththatatdelaytimeof400ns.Thetime-dependentrelative
concentrationofN(4s)atomsinl.OTorrofO2thusobtainedisplottedinFig.5.2b
74
(OPenCircles).Forcomparison,thetime-dependentconcentrationofN(4s)atomsin
l･OTorrofArisalsoplottedinFig.5.2b(OPentriangles).
The
center-Oflmass
collision
energy
between
hotN(4s)and
O2bath
gas
moleculeisroughlycalculatedtobe32/46Et,WhereEtisthetranSlationalenergyof
N(4s)atomsintheLAB丘ame.InthedelaytimesrangeShorterthanlOOns,about
one-thirdofcollisionsbetweenN(4s)andO2areeStimatedtohavecenter-Ofこmass
COllisionenergieshigherthantheactivationenergyforreaction(5.1),∼0.24eV(=5.5
kcalmol.1).However,aSShowninFig.5.2b,nOnOtabledecreasewasobservedfor
N(4s)concentrationsinO2gaSeVenintheshortdelaytimerange,COmParedwiththe
concentrationofN(4s)atomsinArgas.Thismaybeduetomuchsmallercross
SeCtionsfbrreaction(5.1)atthecenter-OflmasscollisionenergiesofaboutO.24-0.6eV
thanthetranSlationalrelaxationcrosssection.
5･4Modelcalculationsfbrhardspherecollisionradii
ThecollisionalrelaxationofsuprathermalN(4s)atomswassimulatedusingan
elastichard-SPherecollisionmodelwithaMonteCarlomethod･Usingthismodel
Calculationmethod,WePreViouslystudiedthecollisionalrelaxationofsuprathermal
O()D)[17,18].TheexperimentalresultsfbrtranSlationalrelaxationofsuprathermal
O(1D)incollisionswithbathgasesofN2andO2mOleculesandraregaSatOmSWere
SuCCeSSfu11yreproducedbythesimulation.Detailofthesimulationwasdescribedin
OurPreViouspqper[19]･Therefore,thesimulationprocedureisonlybrieflyexplained
here.ThevelocityofN(4s)atomsatt=0foreachtrqiectoryisgeneratedrandomlyso
thatithasthenascentdistributionobtainedfromtheDopplerpro丘1e･Thevelocityof
thebathgasesisgeneratedrandomlyforeverycollisionsothatithasaMaxwellian
distribution
at295K･The
maximumimpact
parameter,bmax,is
the
equalto
hard-SPhereradius,d=r(N)+r(bathgas),Whichhasbeentakenasaparametertofitthe
Simulation
to
the
experimentalvalues
of<Et>･TheilnPaCt
ParameterS,aZimuthal
angles,andcollisionintervaltimeforeverycollisionarealsogeneratedrandomlywith
their
respective
appropriate
weightfunctions.The
velocity
ofN(4s)aRer
every
COllisionwiththoserandomlygeneratedconditionsiscalculated.Thetr毎ectoryof
eachN(4s)atomiscalculatedfbrsequentialcollisionsuntilthetimeexceedslOOOns
undertheconditionofl.OTorrofbathgases,thatis,1000ns･Torr.A氏ercalculations
Ofupto50000trqjectories,thetranslationalenergydistributiol10fN(4s)intheLAB
75
framewasobtainedateachdelaytlmeuPtOlOOOns･Torr.
Figure5･3showsacomparisonbetweentheexperimentalresultsandmodel
calculationsfortheln[(<El(t)>-<Etth>)/(<Et(0)>-<Etlh>)]valuesasafunctionof
delaytime,Where<Et(t)>istheaveragetranslationalenergyofN(4s)intheLABftame
atdelaytimet,<Et(0)>istheaveragenascenttranslationalenergyofN(4s)formedin
thephotolysisofNO2at193nmand<Etth>istheaveragethermalenergyat295K･
Open
are
circles
ones
simulated
results
with
Doppler
ofthe
the
hard
sphere
curvesare
pro鎖1e measurements･Solid
collision
best-nt
model.The
for
Values
hard-SPherecollisionradiiwere(3.2±0.2),(3.0±0.2),(2.4±0.1),and(2.7±0.1)Åfor
N(4s)+N,,02,HeandAr,reSPeCtively.Thethermalizationcrosssectionvalues(7td2)
weredeterminedtobe(3.2±0.4),(2.8±0.4),(1.8±0.2)and(2.3±0.2)inunitsoflO-15
cm2forthebathgasofN2,02,HeandAr,reSPeCtively･Inthesemodelcalculations
Only
elastic
collisions
were
takeninto
account,althoughthe
can
relaxationprocess
includeenergytranSfbrtotheinternaldegreesoffreedomwhenthecollisionpartneris
the
molecule(N2and
O2).Therefore,the
obtained
hard-SPhere
radiifor
these
moleculesareefftctivevalues.ThevalueobtainedinthepresentstudyforN(4s)+N2
COllisionisslightlysma11erthanthatestimatedfrommoleculardi払1Sioncoefncients
(3.5×10.15cm2)[15].Kharchenko
etal.[13]comparedtheenergydistribution
functionsofN(4s)atomscalculatedusingthethermalizationcrosssectionsobtained
fromtheQMcalculationandhardsphere叩PrOXimationforN(4s)+0(3p).They
suggestedthatusageofthehardspherecollisioncrosssectionof6×10-15cm2provided
an
exce11ent
approximation
to
reproducethe
energy
distributionfunction
calculated
usingtheQMcrosssection.Thisvalueislargerthanthoseobtainedinthepresent
StudyforcollisionswithN2,02,ArandHe･
76
(.qJe)倉su茎こコ(s寸)Z
ー1
0
1
ー1
0
1
△v(Cm-1)
Figure5.1.Dopplerpro丘1esofN(4s)atomsatvariousdelaytimesbetweentheNO2
photolysisandN(4s)detectionlaserpulses.Thepeakheightsofthepro丘Iesare
normalized.TherelaxationagentsareN2andO2.PressuresofNO2andN2(orO2)in
thechamberwerellmTorrandl.OTorr,reSPeCtively.TheDopplerpro頁1eatdelay
timet=Owasactua11yrecordedatt=50nswithoutbathgas.
77
(T一〇∈l円呈∧}山V
Su｡○寸【(s寸)Z】＼}【(s寸)Z】
0
200■
0100
300
400
Delaytime(ns)
Figure5.2.(a):TimeevolutionoftheaveragetranSlationalenergy,<E>t,intheLAB
&amefortheN(4s)atomsproduced&omthephotolysisofNO2at193nm.Thevalue
Of<Et>ateach
delaytime
was
obtainedfromthe
analysIS
Ofthe
Dopplerprofi1es,
whichweretakenundertheconditionsofllmTorrofNO2andl.OTorrofO2.Filled
CirclesaretheresultsoftheDopplerpro創emeasurements.Thebrokenlineindicates
thethermaltranslationalenergyat295K,thatis,(3/2)kBT=0.89kcalmol,】.(b):
TimeevolutionoftheconcentrationfortheN(4s)atomswhenthebathgasisl.OTorrof
O2(OPenCircles)andl.OTorrofAr(OPentriangles).Theverticalscaleisnormalized
bytheN(4s)concentrationatdelaytimeof400ns.ErrorbarSindicatelGValuesof
themeasurements.
78
O
【(∧缶Y∧(○)止V)､(∧￡}山V人(エ}山V)】u
T
-2
■3
-40
-1
■2
【3
■4
0200
400
0
200
400
600
DeIaytime(ns)
Figure5.3.Semi-logaritlmicplotsofthetranSlationalenergyratios,1n[(<Et(t)><Etth>)/(<Et(0)>-<Etth>)],VerSuSdelaytimebetweentheNO2PhotolysisandN(4s)
detection,Where<Et(t)>istheaveragetranslationalenergyofN(4s)atdelaytimet,
<Et(0)>istheaveragenascenttranslationalenergyinthephotolysisofNO2at193nm
and<Etth>istheaveragethermalenergyat295K･Opencirclesaretheresultsofthe
Dopplerpro丘Iemeasurements･Solidcurvesaresimulatedonesuslngthehardsphere
collisionmodelwithbest一餌hard-SPhereco11isionradii(seetext)･Thepressureof
eachbathgaswasl･OTorr･ErrorbarsindicatelcTValuesofthemeasurements･
79
RcfbrcnccsfbrChapter5
[l】ClancyR.T.,RuschD.W.,Muhlmann,GeqpjvLS.Res･Lett.,19,261(1992)･
[2]Suskind,D.E.,Strick】and,D.J.,Meier,R.R.,1句eed,T.,Eparvier,F.G.,JGeqp句げ.Res.,
100,19,687(1995).
[3]Barth,C.A.,Farrner,C.B.,Suskind,D.E.,Perich,J.P.,JGeqpわ岱.Resリ101,12489
(1996).
[4]Solo】nOll,S.,ア血〃eJ.勘αCe助f.,31,135,(1983).
[5]Lie-Sevelldsen,0.,Rees,M.,Stamnes,K,Whipple,E.C.,Planel.勘aceSti.,39,929,
(1991).
[6]Schematovith,ⅤⅠ.,Bisikalo,D.Ⅴ,G6rard,J.C.,Geqp匂LS.Res.Lett.,18,1691(1991).
【7]Girard,J.C.,Bisikalo,D.Ⅴ,Shernatovich,ⅤⅠ.,Du托J.W.,JGeqpj叩.Res.,102,285,
(1997).
[8]Dothe,H.,Sharma,R.D.,Du托J.W.,Geqp句LS.Res.Letl.,24,3233(1997).
[9]Swami11athan,P.K.,Strobel,D.F.,Kupperman,D.G.,KrishnaKumar,C.,Acton,L.,
DeMqiistre,R.,Ybe,J.H.,Paxton,L.,Anderson,D.E.,Stricklalld,D.J.,Du托J.W.,J
Ge呼卸∫.月e∫.,103,11579(1998)･
[10]Ba)akrishnan,N.,Sergueeva,E.,Kharchenko,Ⅴ,Dalgarno,A.,JGeqp如.Res.,105,
18549(2000).
[11]Schematovich,ⅤⅠ.,Bisikalo,D.Ⅴ,G6rard,J.C.,Ann.Geqp7w.,10,792(1992).
【12]Sharma,R.D.,Kharchenko,Ⅴ,Sun,Y,Dalgarn0,A.,JGeqp7vLS.Res.,101,275(1996).
[13]Kharchenko,Ⅴ,Tharamel,J.,Dalgarno,A.,JAtmos.SolaT:乃r7:P7w.,59,107(1997).
[14]Kharchenko,V.,Balakrishnan,N.,Dalgarno,A.,JAlmos.Sola7:乃r7:P7DLS.,60,95(1998)･
【15]Morgan,J.E.,Schiff;H.J.,Can.JChem.,47,2300(1964)･
[16]Zal･e,R.N.,Herschback,D.R.,Proc.mEE,51,173(1963)･
[17]Matsumi,Y,Chowdhul≠A.M.S.,JChem.P/り岱.,104,7036(1996).
[18]Tbniguchi,N.,Hirai,K.,1もkahashi,K･,Matsumi,Y,JP7p･Chem･,AlO4,3894(2000)･
[19]Matsumi,Y,Shamsuddin,S.M.,Sato,Y,Kawasaki,M.,JChem.P如.,101,9610
(1994).
80
Chapter6
PhotochemicalreactionprocessesofO(1s)
andtheirimplicationsfbrOHproductionsandairglow
6.1Introduction
ThephotochemicalprocessesofO(ls)atomplayanimportantroleinchemical
physicsandatmosphericchemistry[1]･ForinstanCe,PrOductionoftheO(ls)atoms
and
their
the
chemicalreactionsin
terrestrialatmosphere
upper
haveknown
to
be
relatedtoairglowphenomena[2,3,4]･
TherearetwoenergeticallypossiblepathwaysfbrO(ls)formationfromO3
PhotoysISarOund200nm:
03+hv→0(ls)+02(X3∑g
)(入<234nm)
→0(一s)+02(al△g)(入<196nm).
(6.1a)
(6.1b)
Channel(6.1a)isaspin-forbiddenprocess,Whilechannel(6.1b)isaspin-allowedone･
ExperimentalstudieshaveshownthatO(1D)andO(3p)atomsarethemqjoratomic
oxygenproductsandthatO(1s)istheminoroneintheUVphotolysisofO3arOund200
nm[5,6,7,8,9].Nishidaetal.[9]haverecentlydeterminedtheO()D)quantumyield
丘omO3PhotolysISaSafunctionofphotolysISWaVelengthbetween193and225nm,
andreportedamonotonicdecreaseintheO(lD)quantumyieldvalues丘om225nmto
193nm.NoinformationisavailableonthephotolysISWaVelengthdependenceofthe
quantumyieldofO(ls)formationfromUVphotolysisofO3arOund200nm.Leeetal･
[5]photolyzedO3mOleculesat170-240nmusingthesynchrotronradiationandtriedto
detecttheO(ls)atomsbyobservationofthe557.7-1memission.Theyobservedno
discemibleemission,andreportedanuPPerlimitvalueofthequantumyieldforO(ls)
formation(≦0.1%).
TheO()s)formationfromN20photolysisat193nmisenergeticallypossible
throughthepathway:
(入<211nm).
N20+hv→0(ls)+N2
(6.2)
PhotodissociationproductsfromN20around200nmhavebeenstudiedindetail,and
thequantumyieldsforO(1D),0(3p),andN(4s)productionsare>0.95,(5±2)×10.3,
(2.1±0.9)×10
3[1,10,11,12,13,14],reSPeCtively.Felderetal.[11]reportedanupper
81
1imitvalueofthequantumyieldforO(1s)fbrmation丘･Om193nmphotolysisofN20
molecularbeamtobe≦0.04.
TheO(ls)fbrmation丘･OmH202Photolysisat193nmisenergetica11ypossible
throughthepathway:
(入<213nm)･
H202+hv→0(ls)+H20
TheIUPAC
on
subcommittee
gas
kinetics
data
evaluation
(6･3)
reviewed
the
available
literaturedata[15,16,17]onthephotodissociationprocessesofH202at193nmand
recommendsthequantumyieldsl･70andO･15fbrOHradicalandHatomformation,
respectively[18]･AnupperlimitvaluefbrO(ls)formationwasreportedtobe<0･02
basedonthekineticmeasurements[16].
KineticstudiesonthereactionsofO(ls)withsma11moleculessuchasH2,02,
CO,CO2,N20,03,H20,SF6,hydrocarbons,andchlorofluoromethaneS,havebeen
performedbyseveralgroups[19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]
andreviewedbyScho丘eld[37]･Inpreviousstudies,0(ls)atomsweregeneratedfrom
VUVphotolysis
ofN200rCO2uSlngaPulsedatomicresonancelampandtime
resoIvedkineticmeasurementswereachievedbydetectingtheemissionoftheO(ls-
1D)tranSitionat557.7nm.Highpressureofraregas(mostlyAr)wassometimes
reaction
addedinthe
systemtointensifythe
greenemissionthroughtheexciplex
formationbetweentheraregasandO(1s)atom.Electron-beamirradiationofagas
mixtureofO2inhigh-PreSSureArwasalsoutilizedasasourceofO(ls)tostudythe
reactionofO(ls)withH20,inwhichthe557･7nmemissionwasmonitoredtodetect
O(1s)【30].
Inthepresentstudy,theformationofO(ls)inthephotolysisofO3at193,215
and220nmandthatforN20andH202at193nmhavebeeninvestigated,uSlngthe
vuv-LIFspectroscopyteclmique･ThequantumyieldsofO(1s)inthephotolysisof
O3at193,215and220nmhavebeendetermined･Thequantumyieldmeasurements
havebeenmadebycomparingtheVUV-LIFsignalintensityofO(1s)withthethatof
H(2s)atom
producedin
the193nm
photolysis
which
ofHCl,in
the
H
atom
nuorescencehasbeendetectedbythesameVUV-LIFmethodat121･'56nm･The
upperlimitsoftheformationyieldsofO(1s)&omthephotolysisofN20andH202at
193nm
have
also
been
room:temPerature
reported･The
rate
COnStantS
reactionsO(1s)+02,CO2,H20,03,andHClhavebeendeterminedbyapplyingthe
pulsedlaserphotolysis/VUV-LIFdetectiontechnique･Theatmosphericimplications
82
fbr the
ofthose
experimentalresults
OHradicalproductionandterrestrialalrglow
onthe
emissionhavebeendiscussed.
6.2Experimental
ThedetailsoftheapparatususedinthepresentstudyareshowninChapter2
andhereonlyadescriptionrelatedtothischapterwillbegiven･TheO(1s)atoms
producedfromO3PhotolysISat193,215and220nmwereprobedbytheVUV-LIF
methodat121.76nm,WhichisresonantWiththeelectronictransitionofO(3sIpl←2p
】so).TheH(2s)atomsproduced丘omHCIphotolysisat193,215and220nmwere
detectedbytheVUV-LIFteclmiqueat121･56nm(Lyman-α),Whichisassociatedwith
electrictransitionofH(2p2n←1s2s).ThetunableVUVlaserradiationaround
121.56nmwas
also
same
obtainedwiththe
VUVlaser
experimentalsetupforthe
systemwiththeKr/Arce11andthefluorescencedetectionsystem･
The
O3mOlecules
were
by
prepared
passlng
the
ultra-Pure
O2mOlecules
(>99.9995%,NagoyaKosan)throughacommercialozonizer･Thenumberdensityof
O3mOleculesinthereactionchamberwasdeterminedbyabsorpt10nSPeCtrOmetryat
253.7nm
using
a
mercury
obtainedN20(>99･9%,
penraylamp.Commercially
TakachihoCo.)gaswasusedintheexperimentswithoutfurtherpurification･Aqueous
hydrogenperoxidesolution(30%w/v,Wako)wasgentlydistilledundervacuumand
storedinaglassbulb･TheconcentrationofH202WaSeStimatedtobe>97%丘omthe
measurements
absorption
based
at193and210nm
on
the
reported
absorption
CrOSS-SeCtions[12].
Forthekineticreactionexperiments,gaSmixturesofO3andreactantswere
introducedslowlylntOthereactionchamberwhichwascontinuouslyevacuatedbya
rotarypumpthroughaliquidN2tr叩･0(1s)atomsweregeneratedbyO3Photolysisat
193nm(channe16･1)･WeestimatetheinitialconcentrationofO(ls)produced
photolyticallytobeintherangeOf(2-12)×1010atomscm-3,Whichwasestimated
fromthereportedabsorptioncrosssectionofO3(4･34×10-19cm2molecule-1)【34],the
o(】s)quantumyieldfromO3Photolysisat193nm((2･5±1･1)×10-3)[33],the
photolysislasernuence(9･6×1016photonscm-2),andtheO3COnCentration(7-36
mTorr).Thepartialpressuresofreactantgaseswere4-32Torr(02),7-36Torr
(CO2),5-48mTorr(H20),2-12mTorr(03),and3-54mTorr(HCl)･TheHCl(>
99.9%,Sumitomo
Seika)and CO2(>99.99%,ShowaTansan)gaseswereobtained
83
commerciallyandwereusedwithoutfurtherpuri丘cation･Thedistilledwaterwasused
aRerfreeze-PumP-thawcycles･A11experimentswereperformedat295±2K･
6.3Resultsanddiscussion
6.3.1QuantumyieldsfbrO(1s)fbrmationfromO3photolysisat193,215,and220nm
Figure6･1showsthefluorescenceexcitationspectraforO(1s)andH(2s)atoms
producedinthe193nmphotolysISOfO3andHCl,reSPeCtively･Theatomicline
pronlesoftheO(3sIpl←2pIso)transitionweredirectlydetectedbyVUV-LIFmethod
ar｡｡nd121.76nm,WhilethoseoftheH(2p2巧←1s2s)transitionweredetectedat
121.56nm.ChecksweremadetoensurethattheO(ls)LIFsignalintensitywas
linearlydependentonthephotolysislaserpowerasshowninFigure6･2･Wealso
O(1s)norH
conhnedthatneither
atoms,signalwas
observed
without193nm
photolysislight･Figure6･3showsthefluorescenceexcitationspectrumfortheO(1s)
atomsproducedinthephotolysISOfO3at215and220nm･Thequantumyieldsfor
o(1s)formationintheO3Photolysisatwavelength入,◎01SO3(入),havebeendetermined
bycomparingtheVtN-LIFintensitiesforO(1s)andHatomsproducedinthephotolysis
ofO3andHCl,reSPeCtively･SincethephotolysisofHClat193,215,and220nm
providesHatomswithaquantumyieldofunity[12],theabsolutequantumyieldsfor
o(1s)formation,◎01SO3(193nm),001SO3(215nm),and◎01SO3(220nm),WereObtained
bythefo1lowlngequation:
S｡(lS)(L)IHfHGH｡l(L)[HCl]4H
×1
◎3言IS)(九)=
SH(九)I｡(一S)f｡(一S)G｡,(L)[0,]￠0(1S)'
(6.4)
(at入=193,215,and220nm)
whereSo(lS)(入)andSH(九)arethepeakareasofthenuorescenceexcitationspectraofthe
O(ls)andHatomsinthephotolysisofO3andHCl,reSPeCtively･Io(1S)andI=arethe
probelaserintensitiesattheresonancewavelengthsofO(ls)(121･76nm)andHatoms
(121.56nm),reSPeCtively･fb(1S)and玩arethetransitionprobabilitiesforO(3sIpl←
2pIs｡)andH(2p2Pj←1s2s)opticalexcitation,reSPeCtively･Go3(入)andGHCl(入)
photoabsorption
cross-SeCtions
HClat
ofO3and
respectively.￠0(lS)and￠Hindicate
the
detection
photolysis
efnciencies
wavelength
ofthe
of九,
resonance
fl｡｡,eSCenCe丘｡mtheexcitedstates,0(3sIp.)andH(2p2n),reSPeCtively,Whichare
preparedbytheVUVlaserirradiation･Thevaluesof玩andfb(1S)Weretaken舟omthe
84
NISTatomicspectradatabase[38].ThevaluesofGo3(入)andGJICl(入)weretaken丘om
MolinaandMolina[39]andSanderetal･[12],reSPeCtively･ThevaluesofSo(1S)(入)
and
S]l(入)were obtained
byintegrating
the
atomicline
thefluorescence
shapesin
excitationspectrafbrtheO(ls)andHatoms,reSPeCtively.Underourexperimental
COnditions,the
quenching
ofthe
Becausethetotalpressuresinthe
O
excited
and
H
atoms
bythe
gasesis
negligible.
chamberwerelessthan1.2Torrandtheradiative
decaylifttimesoftheexcitedstatesarelessthanseveralnanOSeCOnds.Thedetection
emciency
of the
PMT
systemis
to
assumed
be
constant
between
the
resonanCe
nuorescencewavelengthsofO(3sIpl-2pIso)andH(2p2n-1s2s)at121.76and121.56
nm,reSPeCtively,Sincethedifftrenceofthewavelengthsisverysmall.Theelectronic
stateo(3sIpl),WhichispreparedbytheVUVlaserexcitationat121.76nm,emitsthe
twotransitionlines,3pIpl→2pIsoat121･76nmand3pIpl→2pID2at99･50rm･
Thelattertransitionisnotdetectedbythephotomultiplierthroughthe
LiFwindow.
TheA-ValuefortheO(3pIp.→2pIso)transitionisAl=2.06×108sec.1andthatforthe
O(3pIpl→2pID2)isA2=5.06×108sec.1.weusedtherelativevaluesofthe
detectionefncienciesasOo(1S)=Al/(41+A2)and￠H=1.
Thevaluesof◎｡ISO3(193nm)=(2.5±1.1)×10-3,◎｡1SO3(215nm)=(1.4±
0.4)×10-4,and◎｡1SO3(220nm)=(5±3)×10-5werethusdetermined,Wherethe
quotederrorswerethe2GStatisticaluncertaintyoftheexperimentaldata.Thereare
twoenergeticallypossiblechannels(6.1a)and(6.1b)forO()s)formationintheUV
photolysisofO3.ObservationoftheO(1s)formationatboth215and220nmisa
cleareVidencethatthespin-forbiddenchannel(6.1a)isresponsibleforO(一s)formation
fromO3PhotolysISatthosewavelengths.Intersystemcrosslngfromtheexcitedsinglet
StatetOatripletstatecorrelatingtothechannel(6.1a)productsordirectphotoexcitation
onto
the
triplet
state(S)can accountforthe
O(1s)formation.Aweak
spin-Obit
interactionbetweentheslngletandtripletexcitedstatesorsmalltransitionprobability
fromthegroundtothetripletstate(S)mayresultintheverysmallquantumyieldfbr
O(1s)formation.Otherspin-forbiddendissociationprocessesofO(lD)+02(X3∑g-),
0(3p)+02(alAg),0(3p)+02(bl∑g')inthephotolysisofozonehavebeenreportedat
longerwavelengths(∼32511m)withthequantumyieldsofO.08-0.10[40].
6.3.2
DoppIcrpromeofO(1s)produced蝕･OmthephotolysisofO3at193nm
DopplerpronleofO(1s)wasanalyzedtoinvestigatetheO(1s)production
85
processin
the
photolysIS
the
OfO3at193nm･Figure6･4shows
nuorescence
excitationspectrumofthetranSlationa11ythermalizedO(ls)atomsandthatofthe
nascento(1s)atomsfromthephotolysisofO3at193nm･ThethermalizedO(1s)
spectrumshowninFig･6･4awasmeasuredwith17mTorrofO3in2TorrofHebufftr
gas,atthetimedelayof3LISbetweenphotolysISandprobelaserpulses･Thenascent
O(ls)spectrumshowninFig･6･4bwastakenwith3mTorrofO3and150mTorrofO2,
atthedelaytimeof70ns･TheFWHMofthespectralpro丘1eofthethermalizedO(ls)
Gaussian
o.54
a
was
6.4a). Assumlng
atoms
cm-1with
shape(Fig
the
Maxwell-BoltzmanVelocitydistributionsforthethermalizedO(ls)atroomtemperature,
theprobelaserlinewidthiscalculatedtobeO･48cm-1･Figure6･4showsthatthe
spectrumOfthenascentO(1s)hasabroaderfbaturethanthatofthethermalizedO(1s)･
ThisisduetoDopplerefftctsoftheO(1s)fragmentvelocitycomponentsalongthe
propagationdirectionoftheprobelaser[41]･WehaveexaminedtheDopplerprofiles
forthemaximumtranSlationalenergyoftheO(ls)atomsproducedinthe193nm
photolysisofO3･FortheO(ls)+02(X3=g-)process(Chamme16･1a),themaximum
possibleDopplershi氏iscalculatedtobeO･89cm-1･Ontheotherhand,fortheO()s)+
02(al△g)process(Channe16･1b),themaximumDopplershi氏iscalculatedtobeO･23
cm･1,WhichcorrespondstothecasethatthewholeavailableenergylSreleasedintothe
solidandtwodashed
tranSlationalfreedominthe193nmphotolysisofO3･Two
curvesinFig･6･4bindicatetheexpectedmaximumspectralshi氏sconvolutedwiththe
probelaserlinewidthfortheO(1s)+02(alAg)(Channe16･1b)andO(1s)+02(X3=g
)
(Channe16.1a)processes,reSPeCtively･Theexperimentallyobtainedspectrumclear1y
indicatesthattherelativelyfastcomponentsoftheO()s)carmotbeexplainedby
channel(6.1b).Thissuggeststhatchamel(6･1a)shouldberesponsibleforO(1s)
formationinthephotolysisofO3at193nm,althoughthecontributionofcharmel(6･1b)
cannotberuledout.Observationofthespin-forbiddenchannel(6･1a)inthephotolysis
･OfO3at193nmisreinforcedwithasma11butnon-negligibleformationyieldofO(1s)
through
charmel(6.1a)atlonger
photolysis
wavelengths
of215and220nm
describedintheprevioussection･
6.3.3Quantumyields伽rO(1s)伽rmationn･OmN20andH202photolysisat193nm
TheO(1s)formation丘･OmthephotodissociationofN20andH202at193nmwas
alsostudiedinthiswork.ThepartialpressuresofN20andH202inthechamberwere
86
as
230andllOmTorr,COrreSPOndingto7･4×1015and3･6×1015moleculescm-3,
respectively･Thesesampleswerephotolyzedat193nm(∼10mJpulse-))･Usingthe
sameeXPerimentalsetup,theO(ls)fbrmation丘omO3Photolysisat193nmwasprobed
justbeforetheN20andH202eXPerimentswereperformed･TheO3COnCentrationin
thechamberwas3.8×1014moleculescm･3asestimatedbytheabsorptlOnSPeCtrOmetry･
TheO(】s)atomsarePrOducedinthe193nmphotolysiswiththequantumyieldof
◎｡ISO3(193nm)=(2.5±1.1)×10-3.weestimatedtheminimumdetectablelimitfor
O(ls)tobe3×108atomscm.3forsignal-tO-nOiseratioofl･
No
discernible
LIF
N20and
observedfrom
signalofrO(1s)was
H202
photolysisat193nmwhilesigni丘cantLIFsignalofO(ls)formationwasobserved丘om
O3PhotolysIS
underthe
sameeXPerimeptalconditions･Consideringtheavailable
absorptioncross-SeCtionsofO3[39],N20[12],andH202[12]at193nm,Wehave
determinedtheupperlimitvaluesofthequantumyieldsforO(ls)formationinthe193nm
photolysisofN20andH202tObe◎01SN20(193rm)≦8×10-5andOoISH202(193nm)≦3
×10-5,reSPeCtively･Inthisstudy,theHatomsproducedfromH202PhotolysISat193
nmwerealsodetectedbytheVUV-LIFmethodat121･56nm･Thequantumyield
measurementwasmadebycomparingtheVUV-LIFsignalintensityofH(2s)atom
producedinthe193nmphotolysISOfH202Withthatproducedinthe193nmphotolysis
ofHCl.TheHatomquantumyieldwasdeterminedtobeO･20±0･03,Wherethe
quotederrorswerethe2GStatisticaluncertaintyoftheexperimentaldata･
Theproductchannelsandtheirbranchingratiosinthephotodissociation
ofN20andH202at193nmaresummarizedinTables6･1and6･2,reSPeCtively･In
thephotolysisofN20at193nm,0(1D)+N2PrOductcharmelisadominantprocess
withthebranChingratiowhichisclosetounityandotherchannelsareminor(Table6･1)･
The
theoreticaland
shownthat
experimentalstudies[42,43,44,45,etC･]have
dissociationofN20around200nmoccursmainlyviathe21A･state,andthatthe
nearbyllAI･state
may
beinvoIvedin
the
dissociationprocess･An
adiabatic
symmetry
correlationdiagramforN20(N-NO,N20,N2-0)systemassumingaCs
suggeststhattheO(1s)formationisnotfavorablefrombothstates[42]･Inthe
photolysisofH202at193rm,thesumofthequantumyieldfbrOH+OHandH+HO2
product
channels
canaCCOuntfor
a
H202loss
uncertaintiesasshowninTable6.2[16,17].
87
quantum
yield
ofl･O
with､the
6.3.4ReactionkineticsofO(ls)withatmosphericmoIcculcs
AtypicalexampleofthetemporalpronleofVUV-LIFintensityofO(】s)
fo1lowlngthe193-nmlaserirradiationofagasmixtureofO3andO2isshowninFigure
6.5.ThepartialpressuresofO3andO2Were15mTorrand750mTorr,reSPeCtively･
ThetemporalVUV-LIFsignalofO()s)exhibitsaninitialjumpduetophotolytic
formationofO(1s)fo1lowedbyaslowdecayduetoitsremoval･Thetranslationa11y
hotO(ls)atomsproduced丘･OmreaCtion(6･1)arethermalizedwithin1LISunderour
experimentalconditions,aSObservedbymeasurementsofthespectralbroadeningofthe
resonanCelineofO(ls)at121･76nm･InthereactionsofO(】s)withthereactants(X),
thetemporalbehaviorofO(ls)atomsinthelongtimedomain(t>1匹S)isgovemedby
thefo1lowlngPrOCeSSeS:
kx
0(ls)+reactantS→PrOducts
(6･5)
0(1s)→loss(bydiffusionandgasmixtureflow)kd･(6･6)
TheO(1s)concentrationasafunctionofreactiontime,[0(1s)]t,Canbeexpressedas
fbllows:
[0(1s)].=[0(1s)]0×eXP(-k,t)
(6･7)
〝=板【Ⅹ】+毎2[02]+払3[03]+れ
(6･8)
[0(1s)]tand[0(1s)]aretheconcentrationsofO(1s)atdelaytimetandO,reSPeCtively･
[X]istheconcentrationofreactantXinthechamber･k'isthedecayrateobservedfor
theO(1s)concentration.Thenon-ZerOinterceptkdatZerOreaCtantPreSSurereSults
fromtheescapeofO(ls)atomsftomtheprobingzone･Single-eXPOnentialdecay
c｡rVeS
Were
Obtained
fbrtemporalpro丘1es
ofO(1s)as
showninFig･6･5･The
pseudo-nrSt-OrderrateconstantHforaparticularreactantpressurewasderivedbya
nonlinearleast-SquareS丘tanalysis･Theresultantdependenceofthedecayrates,kt-
(ko3[03]+kd),OnthenumberdensityofO2forO(1s)+02reaCtionisshowninFigure
6.6.Linearleast-SquareS丘tanalysISOfthedatainFig･6･6yieldedthebimolecularrate
constantOfko2=(2.85±0･31)×10-13cm3molecule-1s-l･Westudiedthereaction
kineticsofO(ls)+02,CO2,H20,03,andHCltodeteminethebimolecularrate
constantSko2,kco2,kH20,ko3andkHClat295±2K･Plotsofthedecayratesversusthe
densities ofthe
reactantsare
Shownin
bimolecular
Figs･6･6and6･7･The
rate
constants,kco2=(3.09±0･29)×10-13,kH20=(6･38±0･38)×10-10,ko3=(4･63±0･45)
×10-10andkHCI=(5.47±0.27)×10-10cm3molecule-1s-l,WereObtainedfromtheslope
of the
best一丘t straightlines･The
quoted
88
uncertainties
of
the
resultsare
the
2cT-Statisticalerrors.
Table6.31iststheroom-temPeraturebimolecularrateconstantSOftheO(ls)
reactions,lnWhichboththeresultsfromthepresentstudyandpreviousstudiesare
includedfbrcomparison.ReactionprocessesofthemetastableO(1s)atomshavenot
beenextensivelyinvestigated.WhileO(lD)atomswhichhavelessenergythan0()s)
reactwithsmallmolecules
veryefncientlylnalmostevery
collision,thekinetics
of
O(ls)appearstobehighlydependentonthenatureofthecollisionpartner[37].
Therateconstantdeterminedinthisstudyat295±2KforO(ls)+02isin
agreementwiththeresults
Within
the
uncertainties
ofAtkinsonandWelge[26]and
associated
aslistedin
Table6.3.The
Capetanakis
result
etal.【34]
obtainedin
the
PreSentStudyisalsoclosetothevaluereportedbySondermannandStuhl[33].The
branchingratiosfortheproductionofO(1D)andO(3p)ftomO(ls)+02WererePOrted
tobeO･31±0･07andO.69±0.07,reSPeCtively[27],Whiletheelectronicstatesofthe
PrOductO2mOleculeareunknown.Inthepresentstudy,therateconstantvaluefbrthe
O(ls)+02reaCtionhasbeenprovidedusingthenovelexperimentalmethodwhichis
difftrentfromthemothodsusedinthepreviousstudies.
Therateconstantkco2deteminedinthisstudyfbrO(1s)+CO2isconsistent
WiththevaluesofBlacketal.[21],Filsethetal.[23],AtkinsonandWelge[26],and
Blacketal･[29]withintheunCertainties･SlangerandBlack[31]studiedtheproduct
charmelsinthereactionofO(1s)+CO2andreportedthebranchingratiosforO(3p)and
O(1D)productionstobeO.37±0.05andO.63±0.05,reSPeCtively.Incomparisonwith
O(1s),thequenchingofO(1D)byCO2isknowntobeextremelyefncientwiththe
room-temPerature
activation
rate
COnStantOfl･1×10-10cm3molecule-1s-1withno
energy[12].Those
observationsareindicative
orlittle
that the
deactivation
mechanismforO(ls)+CO2isdi脆rentfromthatforO(1D)+CO2.
WehavedeterminedtherateconstantkH2｡forO(1s)+H20.Thisisthe丘rst
reportofthereactionrateconstantwithdennitiveerrorlimitsforO(ls)+H20.As
listedinTable6･3,thekH20Valuesinthepreviousstudiesrangedfrom7×10-11to5×
10-10cm3molecule-1s-1･Theresultobtainedinthepresentstudyisclosetothereport
OfSlangerandBlack[31].Averylargerateconstantforthisreactionisindicativethat
reactivescatterlngaSWellasphysICalquenchinglSillCludedintheremovalprocessof
O(ls)incollisionswithH20.SlangerandBlack[31]suggestedthebranchingratiosof
O.30±0.06,0.09±0.06andO.61±0.06fbrproductchannelsO(1D)+H20,0(3p)+
89
H20,andOH+OH,reSPeCtively･
Therateconstantk｡3determinedinthisstudyforO(ls)+03isconsistentwith
theformermeasurementsbyLondonetal.[24]andKorolevaandKhvorostovskaya[28]
withintheunce,tainties.SincetherateconstantforO()s)+03isaslargeasthegas
kineticcollisionlimit,itislikelythatthereactiveprocessestoproduceO+0+02Play
animportantroleinthisreactionaswellasO(lD)′0(3p)formationthroughthephysical
quenchingofO()s).
ForO()s)+HClreaction,therateconstanthasnotbeenreportedbefore,and
thepresentstudyprovidesa丘rstdeterminationofhc]=(5･47±0･27)×10-10cm3
molecule-1s-l.ontheanalogyoftheveryfastO(1s)+03andO(ls)+H20reactions,
itisprobablethatreactivescatteringaswellasphysICalquenchinglSincludedinthe
removalprocessofO(ls)incollisionswithHCl･BothCl+OHandClO+H
productionsareenergetica11yfeasibleasproductchannelsinthereactivescatterlng
PrOCeSS･
6･4Atmosphericimplications
6･4･10Hproductioninthestratosphereandmesosphere
Inthestratosphereandmesospherebelowabout60km,PrOductionofO(1D)
fromUVphotolysISOfO3isfo1lowedbygenerationofchemica11yactivespeciessuch
asoHradicalsthroughthereactionofO(lD)withH20,WhilemostofO(lD)is
quenchedtoO(3p)bycollisionswithairP2andO2)[46]:
0(lD)+H20→20H
O(1D)+N2→0(3p)+N2
0(lD)+02→0(3p)+02.
TheO(1s)atomsproduced丘omO3PhotolysismightgenerateOHradicals
throughthereactionofO(1s)withH20inthestratosphereandmesosphere･The
reactionrateofO(ls)withH20isveryfastwhilethequenchingrateofO(1s)withN2
anO2areratherslow(Table6･4):
0(1s)+H20→PrOducts
O(1s)+N,→0(1Dor3p)+N2
0(ls)+02→0(lDor3p)+02.
ThebranchingforOHformationcharmelinreaction(6･12)wasreportedtobeO･61[31]･
TheatmosphericOHproductionrates丘omO(lD)andO(ls)reactionswithH20asa
90
functionofthealtitudebetween20and60km,Ro]1)DandRo[JIS,havebeenestimated
uslngthefo1lowlngeXPreSSions,reSPeCtively;
た｡.9[H20]Y諾
月諾= ん6.9[H20】+た6.,｡脚去]+た6.‖[02]
×【03]上伸)G｡3(入)鴫｡,(入)瓜
(6.15)
月誌=
た6.12[H20】Y浣
×[03】l叩)G｡3(九)鴫s)(入)瓜
た6.12[H20]+ん6.13脚2]+た｡.14[02]
(6.16)
whereLiswavelength,F(入)isthesolarnuX,Go3(入)istheabsoIPtioncrosssectionof
ozone,◎oIDO3(入)and◎oISO3(入)arethequantumyieldsofO(ls)andO(1D)fromthe
photolysisofozoneat入,reSPeCtively,k6･9,k6･10,k6･11,k6･12,k6･13,andk6･14arethereaction
rateconstantSfbrreactions(6.9),(6.10),(6.11),(6.12),(6･13),and(6･14),reSPeCtively･
TherateconstantSadaptedarelistedinTable6･4･Thek6･12Valuedeterminedinthe
presentstudywasused･Thetemperature-dependentrateconstantsk6･14forO(ls)【34]
andk6.10andk6.11forO(1D)[12]reactionsweretakenintoaccount･Yo=lDandYo=1Sare
molaryieldsforOHformationfromO(1D)+H20reaction(Yo=1D=2)[18]andO(1s)+
H20reaction(YoHIS=1･22)[31]･FortheO(ls)quantumyields,itwasassumedthatthe
yieldsfo1lowlinearfunctionsintherangeS193-215runand215-220nm･Below193
nm,theyieldwasassumedtobe2･5×10-3･Above220nm,mOnOtOnicdecreaseofthe
yieldfrom5×10-5at220nmtozeroat234nmwasassumed･TbevaluesofF(九)are
calculatedusingtheprogrampresentedbyKyllingetal･[47]･TbevaluesoftemperaturedepepdentGo3(九)aretaken丘omthedatapresentedbyMolinaandMolina[39]･Theloss
ofO(1s)isdominantbyreaction(6･14)atallaltitudesbetween20and60km･Radiative
decayandthereactionwithOatomareunlmportantaSthelossprocessesofO()s)inthe
altituderangeOf20-60km･
Figure6.8showsthepercentagefractionoftheOHproductionfromO(1s)+
H20relativetoO(1D)+H20,RoHIS′RoHIDxlOO,aSafunctionofaltitudebetween20
and60kmatmid-1atitudesatnoon(SZA=500),WhereRoHISistheOHproductionrate
丘omO(ls)+H20reactionwhileRoHIDisthat丘omO(1D)+H20reaction･Ithasbeen
fbundthatthemaximumcontributiollOfO(1s)+H20reactionintheOHproduction
ratesappearsat30kmaltitude,andthefractionrelativetoO(1D)+H20reactionis
about2.5%.
Thesolaractinicfluxdistributionandphotoabsorptioncross-SeCtionsofN20
91
andH202reSultinthephotodissociationofthosemoleculesaround200nminthe
stratosphere[12]･Therefbre,WerOughlyhaveestimatedtheupperlimitsoftheO(ls)
productionratefromN20andH202relativetothatfromO3PhotolysIS,aSSumlngthe
wavelength-independentconstantvaluesoftheO(1s)quantumyieldbelowthreshold
wavelengthsforchannels(6･2)and(6･3),8×10-5and3×10-5,reSPeCtively･The
o(ls)productions丘omN20andH202relativetothatfromO3areeStimatedtobe<10-3
and<10-5,reSPeCtively,atallaltitudesbetween20and60km,uSlngthecross-SeCtions
[12],aCtinicflux[47],andnaturalabundanCeS[46]･ThenaturalabundancesofN20
andH202rangefroml･1to270ppbvandfromO･44tollOpptv,reSPeCtively,inthe
altituderangeof20-60km[46].TheO(1s)formationfromN20andH202Photolysis,
evenifitoccurs,isnotslgni丘cantastheOHsourceinthestratosphereandmesosphere･
6.4.2Dayglowemissioninthemesosphereandlowerthermosphere
TheopticalemissionoftheatomictransitionofO(1s-1D)at557･7nmis
knownasagreencomponentindayglow,nightglow,andauroraspectra･Theavailable
databaseonthegreenlinedayglowemissionhasrecentlybeengreatlyexpandedasa
resultofobservationsmadewiththeWINDIIonboardtheUARS[48].TheVERhas
beenobtainedoverthealtituderange80to300km丘omtheWINDIIobservation･The
WINDIIdatashowedthatthepeakVERaround90-100kmaltitudewaslargerbya
factorofthreeormoreinthedaytimethanatnight[48,49,50,51]･Theobservation
indicates
thatfurther
excitation
should
processes
beinvoIvedin
to
addition
the
three-bodyrecombinationprocessofatomicoxygen(Barthmechanism)･TheBarth
mechanismisknowntobethedominantexcitationprocessofthenightglowemission
peakaroundlOOkm[52],thatis,
where
O2*is
0(3p)+0(3p)+M→0;+M
(6･17)
02*+0(3p)→02(Ⅹ3∑
(6･18)
electronically
excited
g)+0(1s),
state(S)ofoxygen
molecule･Shepherdand
co-WOrkers[49,50,51]haveproposedthatphotodissociationofO2bythesolarradiation
between･100and130nm,eSPeCia11yatLyman-β(102･6nm),isprimarysourceofO(1s)
forthisemissionpeakinthedaytime･
wehaveestimatedtheimpactofthedirectformationofO(1s)丘omtheUV
photolysISOfO30nthegreenlinedayglowemission･TheVERisobtainedbytaking
intoaccountthefbllowingprocessesinadditionto.reactions(6･12)and(6･14)atthe
92
altitudeabove50km:
0()s)→0(lD)+hv(557･7run)
(6.19)
0(ls)→0(3p)+hv(297･2nm)
(6.20)
0(ls)+0(3p)→0(1Dor3p)+0(3p)
(6.21)
0(1s)+02(a]△g)→PrOducts･
(6.22)
Assumingthephotochemicalsteady-StateCOnditions,theVERofO(ls)fromO3
photolysis,77(03),Canbecalculatedasafunctionofaltitudebetween50-100kmusing
thefo1lowlngeXPreSSion:
d6.19
り(03)=
[02]+た6.21[0]+た｡.22【02(al△g)】
｣6.19+4.2｡+た｡.12【H20]+た6.14
×[03]l叩)G｡3(畔昭s(九)瓜･
whereA.9andA2｡are
the
Einstein
coefncientsfor
(6･23)
channels(6･19)and(6･20),
respectively,k6.12,k6.14,k6.21,andk6.22aretherateconstantSforreactions(6･12),(6･14),
(6.21),and(6･22),reSPeCtively,and◎01SO3(入)isthequantumyieldofO(ls)&omO3
photolysisat入･TheEinsteincoefncientsandrateconstantsusedinthecalculations
arelistedinTable6.4.ThesolarfluxspectraF(入)weretakenfromShimazaki[53]
andKyllingetal･[47]･Theatmosphericdensitiesandtemperaturesoftheneutral
weretakenfromtheMSISE-90modelatmosphere[54].ThedensitiesofO3Were
calculatedontheassumptionofthephotochemicalsteady-StatebetweenO3andO(3p)･
ThedensitiesofO2(al△g)werecalculatedusingtheVERprofi1eofthedayglowO2(al△g-
X3=J)(0-0)bandreportedbyEvanSetal･[55]･Figure6･9showstheestimatedVER
pro丘IeforO()s)fromO3Photolysisasafunctionofaltitude･ThedaytimeVER
promeobservedbyWINDIIandtheVERpro丘IeforO(ls)producedfromtheBarth
mechanism(6.17)-(6･18)arealsoplottedinFig･6･9fbrcomparison･TheWINDII
emissionprome,WhichwasanalyzedbyShepherdetal･[50],WaSObtainedataSZAof
47.90andthel｡Caltime｡flO.5hr.TheVERpro丘1eofO(ls)producedfromtheBarth
rneChanismwascalculatedusingtheparameterSOfMcDadeetal･【52],Whichwere
｡btained丘｡mthe,｡CketmeasurementsofboththeO(1s)nightglowemissionratesand
atomicoxygendensities･InFigure6･9,tWOdistinctpeakshavebeenidentinedinthe
VERpro丘1eofO(1s)produced丘omtheUVphotolysisofO3,Oneisaround90km
altitudeandtheotherisbelow50km.Thepeaksprobablycorrespondtotwopeaksin
thenumberdensitypronleofO3,Oneisaround85kmandtheotherisaround30km
93
[56,57].ThepeakvalueofVERforO(ls)produced丘omtheO3Photolysisaround90
kmis∼1photoncm･3s-1,Whilethatoftheobservedpronleis∼700photonscm-3s-1･
Thisresultindicatestllatthe
O(ls)formationintheUV
photolysis
Slgni五cantasanexcitationprocessofgreenlinedayglowaround90kmaltitude･
94
ofO3is
not
(s}モ⊃.q｣且倉su望u一
1
0
(slモコ.q｣且倉su望u一
1
0
△v(Cm-1)
Figure6･1･ThefluorescenceexcitationspectraofO(ls)producedfromthephotolysis
ofO3at193nmandHatomsfromHClat193nm,1nWhichtheVUVprobelaser
wavelengthwasscarmedovertheDopplerpro丘1esofeach丘agments･Thedelaytime
betweenthephotolysISandprobelaserpulseswas150ns･ThepartialpressuresofO3
andHClinthereactioncellwere20and4mTorr,reSPeCtively･
95
(slモ⊃.q｣且倉su甲7ニ山コ(s盲
Photo[ysisIaserpower(arb.units)
Figure6.2.LIFsignalintensityforO(1s)versusthephotolysislaserpower･The
photolysislaserpowerwaschangedwhilemonitoringtheO(ls)LIFsignalat121･76
nm.ThetimedelaybetweenthephotolysISandprobelaserpulseswas150nsandthe
pressureofO3inthereactioncellwas20mTorr･Solidlineistheresultsoflinear
weighted丘tanalysISOftheexperimentaldata･
96
1
(.q｣且倉su望u一
5
0
1
(.q｣且倉su望u一
5
0
△v(Cm-1)
Figure6.3･FluorescenceexcitationspectraofO(1s)produced丘omthephotolysisof
o3at215and220nm･Thespectrumwasmeasuredatthepressuresof25mTorrO3
andl.2TorrofO2,andatthetimedelayoflOOnsbetweenthephotolysISandprobe
laserpulses･
97
(b)
Figure6.4.(a)FluorescenceexcitationspectrumofthermalizedO(1s)atoms･The
thermalizedspectrumWaSmeaSuredwith17mTorrO3in2TorrofHebu脆rgas,anda
time
delay
of3トLS
between
photolysIS
and
probelaser
pulses･The
solid
curve
indicatesaGaussianShapewithFWHMofO･54cm-1,Whichntstheobservedspectrum･
(b)FluorescenceexcitationspectrumofnascentO(1s)丘omthephotolysisofO3at193
nm,Whichwasmeasuredatthepressuresof3mTorrofO3and150mTorrofO2atthe
timedelayof70ns･Solidanddashedcurvesindicatetheekpectedmaximumspectral
shi氏s(0.23andO.89cm-1)convolutedwiththeprobelaserlinewidth(0･48cm-1)when
O(1s)+02(alAg)(Channe16･1b)andO(1s)+02(X3=g
assumed,reSPeCtively(SeeteXt).
98
)(Channe16･1a)processeswas
(s}.≡⊃.q｣且倉su茎こコ(s盲
0
5
DeIaytime山S)
Figure6.5.TypicalexampleofthetemporaldecaycurveofO(1s)fo1lowingthe
193-nmlaserphotolysisofthegasmixturecontaining16mTorrofO3in750mTorrof
O2at295K.TheO(1s)atomsweredirectlydetectedbytheVUV-LIFspectroscopy
teclmiqueat121･76nm･
99
4
(TUむSの○こむ扇｣ゝ3占
[Reactant](1017mo)ecuIescm-3)
Figure6.6.Plot
of
pseudo-nrSt-Order-loss
of
O()s)atoms,kx[X],VerSuS
concentrationofthereactants(OPendiamond=02andopeninvertedtriangle=CO2)･
Solidlinesaretheresultsoflinearweighted丘tanalysISOftheexperimentaldata･
100
the
(TUむSsOこ￠扇｣倉崇占
5
【Reactant](1014moIecuIescm-3)
Figure6.7･Plot
ofpseudo一丘rst-Orderloss
ofO()s)atoms,kx[X],VerSuS
concentrationofthereactantS(OPenSquare=H20,OPenCircle=03,andopentriangle=
HCl).Solidlinesaretheresultsoflinearweighted丘tanalysisoftheexperimental
data.
101
the
0
(∈豊むP⊃茎<
0
0
(RoHIS/RoHID)×100
Figure6.8.PercentagefractionofthecalculatedOHproductionfromO(1s)+H20
relative
to
O(1D)+H20,RoHIS/RoHID
xlOO,aS
mid-latitudes(SeeteXt).
102
afunction
ofaltitudein
the
(∈呈むP⊃l≡<
10-1
100
101
102
103
volumeEmissionRate(Photonscm-3s-1)
Figure6.9.ThecalculatedVER(VOlumeemissionrate)pro丘1esofO(1s)produced
fromO3Photolysis(SOlidline)andthatofO(1s)producedbytheBarthmechanism
(dottedline),andadaytimeVERpro丘1eobservedbyWrNDIIfbrasolarzenithangle
(SZA)of47.90andthelocaltimeoflO･5hr(dashedline)[50]･
103
Table
6.1.
Photodissociation
channels
and
their
branching
ratiosin
the
PhotodissociationofN20at193nm･
cham一el入1..resh｡･da
Branchingratiob
N2+0(lD)341
∼1.O
慧ごRe指･
Sanderetal.(2003)･【12]
Greenblattand
N+NO
248
≦8×10
NO
3
Ravishankara(1990)[10]
(2.1±0.9)×10■3
N
Thiswork
N2+0(3p)742
(5±2)×10-3
0(3p)
Nishidaetal.(2004)[14]
N2+0(ls)211
≦8×10-5
0(1s)
Thiswork
N2+0(ls)211
≦0.04
0C
Felderetal.(1991)[11]
N+NO
a.
248
Thermochemicalthresholdforeachchannelinn皿.
b.Quoteduncertaintiesincludethe2G-Statisticalerrors.
c.Felderetal.(1991)[11]detectedthetranSlationalenergydistributionofO
atolnSWithtime-Of-nightmassspectrometryinthemolecularbeam
Photodissociationexperiment･
104
Table
6.2.
Photodissociation
channels
and
their
branching
the
ratiosin
PhotodissociationofH202at193nm･
器;ごRe鈷･
channel入threshoIda慧hing
Vaghiianietal.(1992)[16]
20H(Ⅹ2n)
H+HO2C
325
0(3p)/0(lD)
0.76±0.09
0H
0.61±0.07
0H
Schiffrnanetal.(1993)[17]
0.20±0.03
H
Thiswork
0.25d±0.02
H
Gerlach-Meyeretal.(1987)[15]
0.16±0.04
H
Vag旬ianietal.(1992)[16]
<0.001
0(3p)
Vag坤弧ieJαJ.(1992)[16]
≦3×10.5
0(1s)
Thiswork
<0.02
0(3p)
Vagljianietal.(1992)[16]
555
829/358
+H20
0(ls)+H20
a.
213
ThermOChemicalthresholdforeachcharmelinnm.
b.Quoteduncertaintiesinclude2G-Statisticalerrors･
c.2H+02Channelisalsopossible,入thre,h｡)d=209nm･
d.ThevalueofO.12±0.01whichwasorlglnallyreportedbyGerlach-Meyeretal･
[15]hasbeenmodi丘edusingthenewcross-SeCtionvaluerecommendedbyNASA
[12]andbyNicovichandWine[58]･
105
Table6.3.SummaryoffbrmerandpresentstudiesonthereactionkineticsofO(ls)
withO2,CO2,H20,03,andHClatroomtemperature･
02
ka
O(ls)detectionmethod
Ref§.
1.0×10-13
0(1s→1D)Emissionb
YoungandBlack(1966)【19]
3.2×10-13
O(1s→1D)Emissionb
StuhlandWelge(1969)[20]
5×10-13
O(ls→lD)Emissionb
Blacketal.(1969)【21]
3.7×10-13
O(1s→1D)Emissionb
FilsethandWelge(1969)[22]
(3.6±0.4)×10-13
O(ls→1D)Emissionb
FilsethandStuhl(1970)[23]
(2.57±0.3)×10
O(ls→1D)Emissionb
13
O(1s→1D)Emissionb
2.1×10-13
AtkinsonandWelge(1972)
【26]
Slangeretal.(1972)【27]
Korolevaand
(5±3)×10
CO2
O()s→1D)Emissionb
13
Khvorostovskaya(1973)[28]
(2.58±0.08)×10
13c O(1s→1D)Emissionb
Sondermannetal.(1990)[33]
(2.64±0.16)×10
13 O()s→lD)Emissionb
Capetanakisetal.(1993)【34]
(2.85±0.31)×10
13d VUV-LIF
Thiswork
2.5×10-川
0(1s→lD)Emissionb
YoungandBlack(1966)【19]
4.6×10-13
O(ls→1D)Emissionb
StuhlandWelge(1969)【20]
3×10-13
O(ls→1D)Emissionb
Blacketal.(1969)[21]
O(ls→1D)Emissionb
FilsethandStuhl(1970)[23]
3.9×10-13
O(1s→1D)Emissionb
Londonetal.(1971)【24]
5×10-13
O(1s→lD)Emissionb
Welgeetal.(1971)[25]
(3.31±0.3)×10-13
O(ls→1D)Emissionb
AtkisonandWelge(1972)[26]
(3.8±0.4)×10
O(ls→lD)Emissionb
Blacketal.(1975)[29]
(3.6±0.4)×10
13
13
(3.80±0.22)×10
13 O(1s→1D)Emissionb
Capetanakisetal.(1993)【34]
(3.09±0.29)×10
13d VUV-LIF
Thiswork
106
H20
∼4×10-10
(7.0±3.5)×10
11
(1.27±0.15)×10
O(1s→lD)Emissionb
FilsethandStuhl(1970)【23]
O(3p)detectionf
(6.38±0.38)×10
(5.8±1)×10
FilsethandWelge(1969)[22]
10e O()s→lD)Emissionb
5.0×10-10
03
0(ls→1D)Emissionb
10d VUV-LIF
10
Binghametal.(1976)[30]
SlangerandBlack(1978)[31]
Thiswork
0(1s→lD)Emissionb
Londonetal･(1971)[34]
Korolevaand
(8±3)×10.10
(4.63±0.45)×10
0(ls→】D)Emissionb
Khvorostovskaya(1973)【28]
10d vuv-LIF
Thiswork
vuv-LIF
Thiswork
HCl(5.47±0.27)×10,10d
a･BimolecularreactionrateconstantatrOOmtemPeratureinunitsofcm3molecule-)
s-1.
b･EmissionarisingfromO(ls-1D)transitionat557.7nm.
C.Theerrorlimitsareestimatesof3G.
d.Theerrorlimitsareestimatesof2G.
e.TheerrorlimitsareeStimatesoflG.
f
ProductsanalysiswasperformedwithO(3P)detectionusinganatOmicoxygen
lamp[31].
107
Table6.4.AdoptedreactionrateconstantS(k)andEinsteincoefficients(4)
Reactions
kaandAb
6.9
毎.9=2.2×10
6.10
毎･10=3･2×10
Refb.
10
Sanderetal.(2003)[12]
Sanderetal.(2003)[12]
】1exp(芋)
Sanderetal.(2003)[12]
丘…=1･8×10-‖exp(ギ)
6.14
毎.12=6.38×10●10
Thiswork
毎.13<5×10
Okabe(1978)[1]
17
k6.1.=2.64×10,13exp(ー812+18.2T2､Capetanakisetal.(1993)
[34]
｣6.18=1.26
Martinetal.(1999)[38]
月6.19=7.54×10-2
Martinetal.(1999)[38]
毎.20=2×10
SlangerandBlack(1981)
14
【59]
鬼6.21=2.6×10-柑
KennerandOgryzlo(1982)
【60]
a.incm3molecule-1s.1
b.ins-l
108
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Chapter7
Summaryandfutureperspective
Inthepresentstudy,thehigh-SenSitiveteclmiquesforN(4s)andO()s)detection
usingvacuumultravioletlaser-inducedfluorescence(VUV-LIF)spectroscopyat120･07
minimum
and121.76nm,reSPeCtively,Weredeveloped･The
detectionlimitsfor
N(4s)andO(Is)atomswereestimatedtobe2×109and3×108atomscm-3,
respectively･Usingthenewdetectionteclmiques,SeVeralimportantPhotochemical
reactionsrelatedtoNOxandHOxchemistrylnthemiddleandupperatmospherewas
studied.
TheN(4s)formationprocess丘omUVphotolysisofN20wasstudied･The
quantumyieldfbrN(4s)formationintheN20photolysisat193nmwasdeterminedto
be(2.1±0･9)×10-3･Impactofth?PhotolyticN(4s)andNO(X2Il)production丘om
N20photolysIS
On
chemistry
StratOSPheric
was
explored
uslng
aOne-dimensional
photochemicalmodelwhilethefragmentationwasnotconsideredinformermodel
dissociationchannelwas
calculations.WhentheN(4s)+NO
consideredinthe
photochemicalmodel,anenhanCementOftheNOxproductionrate(upto3%)was
observed,Which
wasfo1lowed
by
a
decrease
ofthe
steady-State
O3COnCentration
throughoutthestratosphere･Theexperimentaltechniqueofpulsedlaserphotolysis
combinedwiththeVUV-LIFdetectionwasappliedforthenrsttimetothekinetic
studiesoftheimportantreactionsofN(4s)inthemiddleandupperatmosphere･The
N(4s)atomswereproducedfo1lowing193nmArFlaserirradiationofNOandNO2･
TheratecoefncientsofN(4s)withNOandNO2at295±2Kweredeterminedtobe
(3.8±0･2)×10-1]and(7･3±0･9)×10-12cm3molecule-1s-l,reSPeCtively･The
competitiveprocessesoftheinelasticcollisionstoproduceNOandtheelasticcollisions
t｡the,malizethetranslationalenergyofN(4s)wasalsoinvestigatedfbrthereactionof
suprathermalN(4s)reactionwithO2atinitialcenter-Oflmasscollisionenergyofabout
O.24-0.6eV.ThesuprathermalN(4s)atomswhichhaveanaveragetranslational
energyofO･92±0･095eVinthelaboratoryflamewereproducedby193nmphotolysis
ofNO2inbathgasofO2･NocleareVidenceoftheNOproductionwasobserved,
whichwillbeexplainedbyarelativelylargevalueofthethermalizationcrosssection
112
theinelastic
COmParedwith
SuPrathermalN(4s)in
co11ision
collisions
cross
section.Thethermalization
withN2,02,He･and
Ar
rates
were
of
experimental1y
determinedforthe丘rsttime･Thosethermalizationratesarecrucialparametersfor
evaluating
the
thermOSPheric
contribution
NO
ofthe
production
reaction
ofsuprathermalN(4s)with
thermalization
rates.The
cross
section
O2inthe
valuesfor
suprathermalN(4s)incollisionswithN2,02,He,andArare(3･8±0･4),(2･8±0.4),(1.8
±0･2),and(2.3±0.2)inunitsoflO
15cm2,reSPeCtively.
TheO()s)formationprocessesfromUVphotolysisofO3,N20,andH202WaS
studied.TheO(ls)formationinthephotodissociationofO,ar0und200nmwas
Observedforthenrsttime,and'thequantumyieldsat193,215,and220nmwas
determinedtobe(2･5±1･1)×10-3,(1･4±0･4)×10-4,and(5±3)×10-5,reSPeCtively.
TheupperlimitvaluesofthequantumyieldsfbrO(1s)productionffomN20andH202
Photolysisat193nmweredeterminedtobe8×10-5and3×10-5,reSPeCtively･The
quantum
yieldfor
H
H202PhotolysIS
atomproductionfrom
at193nm
was
also
determinedtobeO･20±0･03･Thepulsedlaserphotolysis/VUV-LIFteclmiquewas
appliedforthe丘rsttimetothekineticstudiesofO()s)･TheratecoefncientsofO(1s)
WithO2,CO2,H20,03,andHClat295±2Kwasdeterminedtobe(2.85±0.31)×10.13,
(3･09±0･29)×10-13,(6･38±0･38)×10-10,(4･63±0･45)×10-10,and(5･47±0.27)×
10-10cm3molecules-1s-l,reSPeCtively･Basedonthepresentlaboratorydata,theimpact
ofO(1s)formationfromtheUVphotolysisofO30ntheOHproductionthroughO(ls)+
H20reactioninthestratosphereandmesospherewasestimated.Itwasfbundthatthe
relativecontributionsoftheO(1s)+H20reactionagainsttheO(lD)+H20reactionin
theOHproductionshaveitsmaximumat30knaltitudeanditscontributionisabout
2･5%･TheimpactofdirectformationofO(ls)intheUVphotolysisofO30nthe
557･7-nm
dayglow
emissionin
the mesosphereandlower
thermosphere
wasalso
estimated･ThecontributionoftheO(1s)formationintheO3Photolysiswasfoundtobe
OfminorimportanCeaSaneXCitationprocess
of557･7-nm
dayglowaround90kn
altitude.
ThepresentstudyhasdemonstratedthattheVUV-LIFteclmiqueisapowerfu1
tooltoinvestigatetheimportantPhotochemicalprocessesinvoIvingN(4s)andO(1s)in
themiddleandupperatmosphere･Theresultsinthisthesisshowthatthephotolytic
formationofN(4s)andNO&omN20canaCtaSaneWSOurCeOfstratosphericNOx,and
thatthereactionofH20withO(ls)whichisformedfromO3PhotolysiscanaCtaSa
l13
newsourceofstratosphericandmesosphericHOx･Thekineticdata(quantumyield,
ratecoe餓cient,andthermalizationcrosssection)determinedpreciselyinthepresent
Studywillbeimportantfordetailunderstandingofthephotochemicalprocessesrelated
tothe
O3COnCentrationinthemiddleatmosphereand
steady-State
O(ls)dayglow
emissionintheupperatmosphere.
FurtherlaboratorystudiesofthephotochemicalreactionsinvoIvingN(4s)and
O(1s)atomsarenecessaryfbrdetailunderstandingofthechemicalprocessincluding
HOxinthe
NOxand
middleand
thepresent
upperatmosphere.In
rate
study,the
coefncientsforthereactionsofN(4s)withNOandNO2at295±､2Khavebeen
determined.However,thetemperature-dependentratecoefGcientsofthesereactions
are
atmospheric
requiredfor
mesospheric
reaction
to
modelcalculations
processes
the
study
stratospheric
alimited
ofN(4s)atoms.Only
number
and
ofthe
temperature-dependentkineticstudiesforthoseN(4s)reactionshavebeenreported
PreViouslyandagreementbetweentheresultantdataisrelativelypoor･Thepulselaser
Which
has
been
as
approved
developedinthepresent
spectroscopy
PhotolysISCOuPledwiththeVUV-LIF
a
promlSlng
teClmiquefor
study,
kinetic studies
room
at
temperature,isapplicabletothetemperature-dependentkineticstudiesforthereactions
invoIvingN(4s)atomsatatmospherictemperatures.Atemperature-COntrOlledreaction
Chamber
should
be
developed
orlglnallyfor
the
experiments.The
state
art
of_the
teclmiqueoftheVUV-LIFspectroscopywillprovideprecisekineticdataasafunction
OfgastemperatureandclarifythediscrepanCiesreportedinthepreviousstudies.
ThecollisionalrelaxationratesofsuprathermalN(4s)incollisionswithN2and
O2determinedinthepresentstudywillmakeitpossibletoperformmOrePreCisemodel
Calculations
relevant
thermalization
cross
to
the
section
thermospheric
values
NOformation
obtainedin
the
present
processes･Using
study,a
Steady
the
state
tranSlationalenergydistributionsofN(4s)willbecalculatedasafunctionofaltitude.
ToestimatetheimplicationsofthereactionofsuprathermalN(4s)onthethermospheric
NOformation,theenergy-dependratecoefncientsofthereactionofsuprathermalN(4s)
WithO2arealsoneeded･However,nOlaboratorystudydetermlnlngtheenergy-depend
ratecoefncientsofthereactionムfsuprathermalN(4s)withO2hasbeenreported.The
relevantexperimentalteclmiquesincludingtheproductionofsuprathermalN(4s)atom
andthedetectionofthereactionproducts,NOorO(3p),Shouldbeappliedfbrthe
l14
▲
kinetic
studies
ofthe
ofa
reaction･Development
new
to
experimentaltechnique
producesuprathermalN(4s)atomwithoutformationofNOandO(3p)isrequired･
Inthepresentstudy,theimpactofO(1s)formation丘omtheUVphotolysisof
O30ntheOHproductionthroughO(1s)+H20reactionhasbeenestimatedbasedonthe
availableliterature
presentand
data･Since
nolaboratory
study
to
determine
the
temperaturedependenceoftheratecoefncientsofO(1s)withH20hasbeenreported,
theratecoe伍cientsatroomtemperatureobtainedinthepresentstudywasadoptedin
theestimation.Iftherate
coefncient
ofO(ls)+H20reactionhad
asigni丘cant
temperaturedependence,theresultoftheestimationwouldhavechanged･Infuture,
determinationsofthetemperaturedependenceofthereactionsofO()s)withH20will
beperformed･ThestateofthearttechniqueoftheVUV-LIFdetectionofO()s)will
hasapotentialtobeappliedtothetemperature-dependentstudies･
Theexcitationprocessesof557･7-nmdayglowandnightglowemissionsar0und
90-100km
are
stillcontroversial.Thethree-bodyrecombinationprocessofatomic
oxygen(Barthmechanism)isknownasaprimaryexcitationprocessforbothdayglow
and
nightglow
mechanism,three
emission.As
the
excited
state(S)ofmolecular
candidates,02(A3∑｡+),02(Cl∑｡
oxygenin
),and O2(A,3△｡),have
Barth
been
proposedonthebasisofenergyconsiderations･However,nOdirectevidenceaboutthe
molecularquantumStateShasbeenobtained･Beyonddoubt,SuChthespectroscopIC
dataishighlyneededforcompleteunderstandingoftheairglowemissionprocesses･
Furtherexperimentalstudiesfortheenergytransferreactionsofthesecandidatesin
collisionswithO(3p)toproduceO(ls)arerequired.Inthemydissertation,1aboratory
experimentsuslngtheVUV-LIFteclmiquewithatmosphericmodelcalculationshave
beenmadetoclarifyadiscrepanCyinthevolumeemissionratesof557･7-nmdayglow
betweentheobservationandmodelcalculations.Ithasbeenfoundthat,forthe丘rst
time,thecontributionoftheO(1s)formationintheO3PhotolysisisofminorimportanCe
asaneXCitationprocess.TheO(ls)formationintheVUVphotolysisaroundlOO-130
rmwasalsoreportedtobeacandidateforexcitationprocess･Thequantumyieldsfor
O(1s)formationintheVUVphotolysisofO2arOundlOO-130nmhavenotbeenwell
known.TheVUV-LIFtechniqueisapplicabletotheprecisedeterminationsofthe
quantumyieldsforO(1s)formationintheVUVphotolysisofO2arOundlOO-130nm･
115
Acknowledgments
The
present
work
was
carried
out
at
Laboratory(STEL),NagoyaUniversityandwas
Proftssor
Yutaka
Solar-TerrestrialEnvironment
the
achievedunderthe
Matsumi･Fore血ost,the
author
a
owes
supervision
specialthanks
to
of
Prof
YutakaMatsumifortheopportunitytoworkonthisprq]eCtandfbrprovidingguidance,
COmmentS,SuggeStions,andencouragementsthroughthework･Dr.KenshiTakahashi
(STEL,Nagoya
Univ･)is
also
acknowledgedfor
his
help,guidanCe,advice,and
encOuragementS･
TheauthorwouldliketothanktoProfKazuoShiokawa(STEL,NagoyaUniv.),
ProflAkiraMizun0(STEL,NagoyaUniv･)andDr.NoriyukiTanaka(Univ.Alaska
Fairbanks)fortheirvaluablecommentSOnthemanuSCript.Theauthorisgratefu1to
Pro￡Masahiro
Kawasaki(Kyoto
Fairbanks),and
Univ･),ProflWilliamR.Simpson(Univ.Alaska
Dr･TimothyJ･Wallington(Ford
Motor
Co.)for
providing
the
OPPOrtunitiestolearnexperimentalskillsintheirlaboratory･
The
author
wishes
to
acknowledge
Dr･NoriTaniguchiand
Pro￡Sachiko
Hayashida(NaraWomen'sUniv･)forprovidingthemodelcalculationsinChapter3and
ProflKazuhiko
Shibuya(TokyoInstituteofTeclm0logy)for丘uitfuldiscussions
photolyticN(4s)formationsinChapter4.Theauthorwouldliket｡thal止theteclmical
Staf穐oftheSTEL;Mr･NoriiiToriyama,Mr.HidehikoJindou,Mr.MasahiroKaneda,
Mr･HiroshiNakada,andMr･MasahiroNagatanifortheirteclmicalassistance･Special
thanksaredueto
allthememberoftheMatsumilaboratoryforthemanyfruitfu1
discussionsandassistanCe.
Fina11y,Iamgratefu1tomyfamilyfortheirsupportandencouragements.
on