Pyrazine, nonadiabatic quantum dynamics

Thoss M, MUler WH, Stock G (2000) Semiclassical description of nonadiabatic quantum dynamics AppUcation to the Si - S conical intersection in pyrazine. J Chem Phys 112 10282-10292... 

Shalashilin DV (2010) Nonadiabatic dynamics with the help of multiconfigurational ehrenfest method improved theory and fully quantum 24d simulation of pyrazine. J Chem Phys 132(24) 244111... 

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. 

Nonadiabatic So S2/Sj Absorption Spectrum of Pyrazine Mostofthe semiclassical theoretical models have been developed in the hmit of a dynamics taking place on a single electronic PES. In order to apply semiclassical methods to nonadiabatic dynamics, further generalization is needed and it is necessary to write down a Hamiltonian with a well-defined classical limit. In this context, the problem of the description of discrete quantum degrees of freedom (electronic states) can be tackled in two steps the first is a mapping onto continuous variables, and the second is a semiclassical treatment of the resulting problem [94,95]. These methods have been recently reviewed by Stock and Thoss [96]. 

---