Vibrational coherence dynamics

The rate constants of the vibrational coherence dynamics such as vibrational coherence transfer can be derived by using the same interaction model used in Eq. (130). For example, the rate constants of the vibrational coherence transfer processes from bv + 1 ->bv + 1 to bv -+bi/ and from bv —l 1 to bv ->bv are, respectively, given by... 

Zhu I, Wdom A and Champion P M 1997 A multidimensional Landau-Zener description of chemical reaction dynamics and vibrational coherence J. Chem. Phys. 107 2859-71... 

Related results of promotion (catalysis) and inliibition of stereonuitation by vibrational excitation have also been obtained for the much larger molecule, aniline-NHD (CgH NHD), which shows short-time chirality and stereonuitation [104. 105]. This kind of study opens the way to a new look at kinetics, which shows coherent and mode-selective dynamics, even in the absence of coherent external fields. The possibility of enforcing coherent dynamics by fields ( coherent control ) is discussed in chapter A3.13. 

Vos M H, Jones M R, Hunter C N, Breton J, Lambry J C and Martin J L 1996 Femtosecond spectroscopy and vibrational coherence of membrane-bound RCs of Rhodobacfe/ sp/raero/des genetically modified at positions M210 and LI 81 The Reaction Center of Photosynthetic Bacteria—Structure and Dynamics ed M E Michel-Beyerle (Berlin Springer) pp 271-80... 

Hayashi M, Yang T-S, Yu J, Mebel A, Chang R, Lin S H, Rubtsov I V and Yoshihara K 1998 Vibronic and vibrational coherence and relaxation dynamics in the TCNE-HMB complex J. Phys. Chem. A 102 4256-65... 

M. Giihr, in Coherent Dynamics of Halogen Molecules in Rare Gas Solids, ed. by S. De Silvestri, G. Cerullo, G. Lanzani. Coherent Vibrational Dynamics (CRC, Boca Raton, 2007), p. 173... 

Figure 14. (a) Potential-energy surfaces, with a trajectory showing the coherent vibrational motion as the diatom separates from the I atom. Two snapshots of the wavepacket motion (quantum molecular dynamics calculations) are shown for the same reaction at / = 0 and t = 600 fs. (b) Femtosecond dynamics of barrier reactions, IHgl system. Experimental observations of the vibrational (femtosecond) and rotational (picosecond) motions for the barrier (saddle-point transition state) descent, [IHgl] - Hgl(vib, rot) + I, are shown. The vibrational coherence in the reaction trajectories (oscillations) is observed in both polarizations of FTS. The rotational orientation can be seen in the decay of FTS spectra (parallel) and buildup of FTS (perpendicular) as the Hgl rotates during bond breakage (bottom). 

B. Kohler Prof. Fleming, your experimental results clearly indicate that in the case of I2 in hexane the vibrational coherence of an initially prepared wavepacket persists for unexpectedly long times. However, quantum dynamical calculations show that wavepacket spreading due to anharmonicity can be very substantial even for isolated molecules... 

On the right-hand side of Eq. (3.65), the first, second and third terms describe the dynamic behavior of paca due to the vibronic coherence dynamics, non-adiabatic transitions and vibrational relaxation, respectively. Several cases can be considered. First, if the vibrational relaxation is much faster than electronic processes, then... 

Figure 5.4, one can easily understand why the interfacial electron transfer should take place in the 10-100 fsec range because this ET process should be faster than the photo-luminescence of the dye molecules and energy transfer between the molecules. Recently Zimmermann et al. [58] have employed the 20 fsec laser pulses to study the ET dynamics in the DTB-Pe/TiC>2 system and for comparison, they have also studied the excited-state dynamics of free perylene in toluene solution. Limited by the 20 fsec pulse-duration, from the uncertainty principle, they can only observe the vibrational coherences (i.e., vibrational wave packets) of low-frequency modes (see Figure 5.5). Six significant modes, 275, 360, 420, 460, 500 and 625 cm-1, have been resolved from the Fourier transform spectra of ultrashort pulse measurements. The Fourier transform spectrum has also been compared with the Raman spectrum. A good agreement can be seen (Figure 5.5). For detail of the analysis of the quantum beat, refer to Figures 5.5-5.7 of Zimmermann et al. s paper [58], These modes should play an important role not only in ET dynamics or excited-state dynamics, but also in absorption spectra. Therefore, the steady state absorption spectra of DTB-Pe, both in...

The relaxation and coherence dynamics contributions to Eq. (128) within the BOA approximation are considered. For this purpose, g = (a, ), m — (b, a ), and n — (c, w ) are defined, where, for example, u represents the vibrational quantum numbers of the vibrational modes of the electronic ground state. For the electronic coupling between the two excited states, it is assumed that the interaction Hamiltonian is given by H — c)Jcb(Q)(b + h.c. where Q denotes the normal coordinate. The coupled GMEs, for example, for pbv,cw can be written as [67]... 

Finally, the technique is one that permits the direct characterization of dynamical processes on a picosecond time scale. This ability to ascertain the temporal details of IVR is important in that it is necessary to the observation of vibrational coherence and to a complete understanding of the nature of the IVR process. 

B. Hartke, R. Kosloff, and S. Ruhman, Large amplitude ground state vibrational coherence induced by impulsive absorption in Csl. A computer simulation. Chem. Phys. Lett. 158 223 (1986). R. Kosloff, Time-dependent quantum-mechanical methods for molecular dynamics, J. Phys. Chem. 92 2087 (1988). 

The coherent dynamics are reversible since the system is isolated and there are no bath modes in the simplified one-dimensional model. Therefore, if the two electronic states are coherently excited by a Unearly polarized pulse, the dynamic behaviors are invariant with respect to change in the direction of polarization, = 1 (e+) or = —1 (e ). Time-dependent behavior of PcuiW with e+ (e ) is the same as Pbo,w t) with = — 1 ( = 1). In real molecules with many vibrational degrees of freedom, the invariance is broken, and dephasing time of the vibrational coherence in lower excited state b is shorter than that in higher state c because multimode effects induced by potential couplings and/or anharmonicity play a much more dominant role in lower state b than in higher state c. 

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