Photoisomerization, ultrafast dynamics

The primary photoreactions in the PYP have been experimentally studied both in the protein and in solution environments. The initial structural change of PYP was directly observed by time-resolved x-ray crystallography. Ultrafast fluorescence spectroscopy was performed on the initial process of the photoreaction of PYP. It was shown that the photoisomerization reaction of the PYP chromophore is completed within 1 ps. The initial photoreaction processes were analyzed by using time-resolved spectroscopic data. Although the reaction of the PYP chromophore in solution environments has been studied by several groups, the characterization of the dynamics in these environments is not fully understood. 

Time-resolved femtosecond absorption, fluorescence, IR, and Raman spectroscopy elucidate the molecular structure evolution during ultrafast chemical reactions [7-11]. The technique provides in real time direct insight into the structural dynamics of various systems including photoisomerization. In this chapter, we briefly describe modem methods of studying photochemical and photophysical processes that have been employed or can be employed in the stilbene photophysics and photochemistry. 

In this chapter we survey characteristic features of time-dependent quantum wave-packet dynamics on conically intersecting potential-energy (PE) surfaces. The focus will be on the fully microscopic description of nontrivial dynamical processes such as ultrafast internal conversion and photoisomerization, as well as vibrational energy redistribution and dephasing. The quantum dynamics calculations discussed in this chapter are... 

The goal of this review is to critically compare — from both a concep-tional and a practical point of view — various MQC strategies to describe non-Born-Oppenheimer dynamics. Owing to personal preferences, we will focus on the modeling of ultrafast bound-state processes following photoexcitation such as internal-conversion and nonadiabatic photoisomerization. To this end, Sec. 2 introduces three model problems Model I represents a three-mode description of the Si — S2 conical intersection in pyrazine. Model II accounts for the ultrafast C B X internal-conversion process in the benzene cation, and Model III represents a three-mode description of ultrafast photoisomerization triggered by a conical intersection. Allowing for exact quantum-mechanical reference calculations, all models have been used as benchmark problems to study approximate descriptions. 

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