Observation of Coherent molecular oscillation : Herzberg-Teller type Wave Packet Motion in Porphyrin J-aggregates MIYASAKA Lab. Tetsuro KATAYAMA

Contents “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 Coherent molecular oscillation Franck-Condon type Wave Packet Motion Herzberg-Teller type Wave Packet Motion

Introduction N. F. Scherer, et al., JCP,1993, 99, 153 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 (I 2 )

Coherent molecular oscillation Probe Pump Detector Delay Time Sample 0 0 t t A ⊿ A ⊿ τ ･ Photoinduced absorption ･ Photo-bleaching, stimulated emission Pump-probe spectroscopy 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 Nucleus separation ･ The curvature is the same. ･ Equilibrium nuclear position is different. ･ Coherent oscillation of transient absorption and stimulated emission are observed ･ Raman transitions causes wave packet motion in the ground state which can be observed in the photo-bleaching excited state ground state 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 oscillate

Overtone was observed at 526nm probe for iodine 580 nm pump 580 nm probe 580 nm pump 526 nm probe 211 cm 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 524 nm Center Turning point 580 nm,480 nm I 2 excited state energy surfaces ground state N. F. Scherer, et al., JCP,1993, 99, 153

Theory Herzberg-Teller type wave packet motion Energy Nucleus separation ･ 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 moment depends on the wave packet position μ+δμ μ μ-δμ Herzberg-Teller type wave packet motion ： ヘルツベルグテラー型波束運動 constant

Two types of wave packet motion Wavelength ⊿ Franck-Condon type Herzberg-Teller type A

Experimental Sample Tetraphenylporphine tetrasulfonic acid ( TPPS 4 ) ～ 2nm J-aggregate R. Rotomskis et al J. Phys. Chem.B, 2004, 108, 2833 J-aggregate ： Ｊ会合体

AFM image of Macroscopic TPPS 4 J-aggregates AFM ： 原子間力顕微鏡法 (AFM image) (Optical microscopy) Optical microscopy ： 光学顕微鏡 R. Rotomskis et al J. Phys. Chem.B, 2004, 108, 2833

Stationary absorption and fluorescence H.Kano.et at.Journal of the Chinese Chemical Society, 2000, 47, 859 Stokes shift is very small (>20meV)

Transient absorption spectrum Photo-bleaching and stimulated emission Transient absorption 320fs

Probe wavelength dependence of the coherent oscillation Overtone wasn’t observed Amplitude Reversed at ～ 1.78eV

Resonance Raman spectrum ruffling mode It is attributed to out-of-plane ruffling mode

Frequency dependence of the initial phase and amplitude Initial phase is constant Amplitude is reversed around 1.78eV(697nm) It might not be Franck-Condon type

Oscillation was observed in the integrated signal Oscillation was also observed in the integrated signal from 1.65 to 1.91eV(752nm to 649nm) It might not be Franck-Condon type 247cm -1

Justification of Herzberg-Teller type 1 Stokes shift was small(>20meV) 2 Over tone wasn’t observed at any wavelength 3 Amplitude was reversed around 1.78eV but phase was constant. 4 Coherent oscillation was also observed 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.

vibration : Window function

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 Probe Pump Transmittance Detection Delay Time Sample

･ 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,

Theory Herzberg-Teller type μ μ+δμ － δμ +δμ μ μ

Why does a wave packet form?

Results ＆ Discussions Stationary absorption T. Ogawa et al..Chemical Physics Letters,2005,408,186 J-band (J-aggregate) (Monomer) The laser spectrum

Resonance Raman spectrum