Katsuki Okuno Miyasaka Laboratory Introduction Vision System Photoisomerization of Retinal in Rhodopsin Experimental Ultrafast Laser Spectroscopy Experimental setup Results Theory Calculation of Molecular Properties Calculation of Trajectory Summary Rod cell: works in dark, detects only brightness Cone cell: works in bright, detects colors http://www.tb.phys.nagoyau.ac.jp/~ayamada/nagare.html Motivation http://www.tb.phys.nagoya-u.ac.jp /~ayamada/rhod_conf.html Transient Absorption Spectroscopy detector Pump pulse Probe pulse t Sample Advantages （1） detection various species such as electronic excited state, ground state, ion radical and radical. （2） identification of intermediates by comparing with known spectra. （3） quantitative information about reaction dynamics if molar absorption coefficient is known. （4） high temporal resolution. Transient Absorption Spectroscopy • Intermediate species • Reaction profile • Time constant Based on Schrödinger Equation Hˆ Y = EY 1 electron approximation (Molecular Orbital: MO method) Wavefunction of system is represented by Slater determinant. Y= y1 (t1 ) y 2 (t1 ) 1 y1 (t 2 ) y1(t 2 ) n! y1(t n ) y1 (t n ) n : number of electron y : molecular orbital y n (t1 ) y n (t 2 ) y n (t n ) Hartree-Fock Equation Determination of Molecular Orbital(y) Properties of Molecule molecular orbital energy total energy molecular structure excitation energy transition dipole etc. left spectrum: experimental result right spectrum: theoretical prediction → almost consistent Initial process in vision is efficient and rapid photoisomerization of retinal in rhodopsin. Ultrafast laser spectroscopy with high temporal resolution revealed that photoisomerization of retinal occur via conical intersection between S1 and S0 potential energy surface. Theoretical prediction for dynamics was consistent with experimental results.
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