Observation of Coherent molecular oscillation : Herzberg-Teller type Wave Packet Motion in Porphyrin J-aggregates MIYASAKA Lab. Tetsuro KATAYAMA Contents Coherent molecular oscillation Franck-Condon type Wave Packet Motion Herzberg-Teller type Wave Packet Motion “Observation of Herzberg－Teller-type Wave Packet Motion in Porphyrin J-Aggregates Studied by Sub-5-fs Spectroscopy” H. Kano, T. Saito,and T. Kobayashi . J. Phys. Chem. A, 2002, 106, 3445 Introduction Coherent molecular oscillation observed by femtosecond transient spectroscopy Coherent molecular oscillation ： コヒーレントな分子振動 Iodine ： ヨウ素 (I2) N. F. Scherer, et al., JCP,1993, 99, 153 Coherent molecular oscillation Pump-probe spectroscopy A Pump ⊿ Detector A Probe t 0 ･Photoinduced absorption ⊿ 0 τ Delay Time t Sample ･Photo-bleaching , stimulated emission Photoinduced (Transient) absorption ： 過渡吸収 Stimulated emission ： 誘導放出 Photo-bleaching ： ブリーチ Franck-Condon type wave packet motion Linear coupling assuming harmonic oscillator Energy excited state ground state ･The curvature is the same. ･Equilibrium nuclear position is different. ･Coherent oscillation of transient absorption and stimulated emission are observed oscillate ･Raman transitions causes wave packet motion in the ground state which can be observed in the Nucleus separation photo-bleaching Franck-Condon type wave packet motion ： フランクコンドン型波束運動 Raman transitions ： ラマン遷移 Equilibrium nuclear position ： 平衡核間距離 Overtone was observed at 526nm probe for iodine 580 nm pump 580 nm probe 580 nm pump 526 nm probe 211 cm-1 420 cm-1 Overtone ： 倍音 N. F. Scherer, et al., JCP,1993, 99, 153 Why was overtone observed ? Typical Franck-Condon type wave packet motion 580 nm ,480 nm I2 excited state energy surfaces Turning point 524 nm ground state Center N. F. Scherer, et al., JCP,1993, 99, 153 Theory Herzberg-Teller type wave packet motion Energy μ+δμ μ-δμ μ ･The curvature is the same. ･No displacement between the equilibrium position. ･Transition frequency do not depend on the wave packet position. ･In Herzberg-Teller type model . Transition dipole constant moment depends on the wave packet Nucleus separation position Herzberg-Teller type wave packet motion ： ヘルツベルグテラー型波束運動 Two types of wave packet motion Herzberg-Teller type A Franck-Condon type ⊿ Wavelength Wavelength Experimental Sample Tetraphenylporphine tetrasulfonic acid ( TPPS4 ) J-aggregate ～2nm J-aggregate ： Ｊ会合体 R. Rotomskis et al J. Phys. Chem.B, 2004, 108, 2833 AFM image of Macroscopic TPPS4 J-aggregates (AFM image) AFM ： 原子間力顕微鏡法 (Optical microscopy) Optical microscopy ： 光学顕微鏡 R. Rotomskis et al J. Phys. Chem.B, 2004, 108, 2833 Stationary absorption and fluorescence Stokes shift is very small(>20meV) H.Kano.et at.Journal of the Chinese Chemical Society, 2000, 47, 859 Transient absorption spectrum Transient absorption 320fs Photo-bleaching and stimulated emission Probe wavelength dependence of the coherent oscillation Amplitude Reversed at～1.78eV Overtone wasn’t observed Resonance Raman spectrum It is attributed to out-of-plane ruffling mode ruffling mode Frequency dependence of the initial phase and amplitude Initial phase is constant It might not be Franck-Condon type Amplitude is reversed around 1.78eV(697nm) Oscillation was observed in the integrated signal Oscillation was also observed in the integrated signal from 1.65 to 1.91eV(752nm to 649nm) 247cm-1 It might not be Franck-Condon type Justification of Herzberg-Teller type 1 Stokes shift was small(>20meV) 2 Over tone wasn’t observed at any wavelength Amplitude was reversed around 1.78eV 3 but phase was constant. Coherent oscillation was also observed 4 from integrated signal Summary The wave packet observed in the present study can be classified as a Herzberg-Teller type in contrast with the frequently studied conventional Franck-Condon type. : Window function vibration X-ray Crystallography Ⅰ X-ray Crystallography Ⅱ How know formation of j-aggregate? J-band Dynamic IntensityBorrowing -Vibronic coupling -Configration interaction Vibronic coupling parity-forbidden a vibration of the molecule can destroy the Inversion symmetry The removal of the centre of symmetry gives rise to a vibronically allowed transition. Experimental Setup Laser system Introduction Pump-Probe Spectroscopy Transmittance Detection Pump Probe Sample Delay Time ･What is Window function ? J-aggregate Why is Stokes shift small ? Frenkel exiciton : TPPS : Transition dipole moment Frenkel exiciton make a mode strong Atkins,D.L. et al ,J. Phys. Chem., 1996, 100, 14391 Problem Really was it observed ? E.A.Carson,et al.,J.phys.Chem.A 2004,108,1489-1500 Theory Herzberg-Teller type +δμ －δμ μ+δμ μ μ μ Why does a wave packet form? Results ＆ Discussions Stationary absorption The laser spectrum J-band (J-aggregate) (Monomer) T. Ogawa et al..Chemical Physics Letters ,2005,408 ,186 Resonance Raman spectrum
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