Several Semiclassical Approaches to Time-resolved Spectroscopy


  • Jiří Vaníček Ecole Polytechnique Federale de Lausanne (EPFL) Institut des Sciences et Ingenierie Chimiques Laboratory of Theoretical Physical Chemistry EPFL SB ISIC LCPT, BCH 3110 CH-1015 Lausanne, Switzerland.



Dephasing representation, Fidelity amplitude, Phase averaging, Semiclassical approximation, Time correlation function, Time-resolved stimulated emission


Ultrafast spectroscopy allows molecular dynamics to be resolved on the femtosecond time scale. Whereas such short time scales obviously pose many experimental challenges, they provide an opportunity for semiclassical methods, which are naturally suited for short time dynamics. Here we review several semiclassical approaches for evaluating vibrationally resolved electronic pump-probe spectra, starting with the simplest, 'phase averaging' or 'dephasing representation'. We continue by discussing several methods developed in our group that allow increasing the efficiency (the cellular dephasing representation) and accuracy (cellular dephasing representation with a prefactor) and end with the Gaussian dephasing representation, which, despite its semiclassical origins, converges to the exact quantum result. The merits as well as shortcomings of the different approaches are demonstrated on time-resolved stimulated emission spectra of NCO and pyrazine.