Jiri Varicek

Prof. Jiri Varicek, Laboratory of Theoretical Physical Chemistry, École Polytechnique Fédérale de Lausanne,  http://lcpt.epfl.ch/vanicek

Increasing the Efficiency and Accuracy of Time-resolved Electronic Spectra Calculations

Joint Quantum Sciences Seminar (in Chemistry)

Abstract:  Rigorous quantum-mechanical calculations of coherent ultrafast electronic spectra remain difficult. I will present several approaches developed in our group that increase the efficiency and accuracy of such calculations:  First, we justified the feasibility of evaluating time-resolved spectra of large systems by proving that the number of trajectories needed for convergence of the semiclassical Dephasing Representation is independent of dimensionality. This method was accelerated with the Cellular Dephasing Representation in which the number of trajectories is further drastically reduced. The accuracy of potential energy surfaces was increased by combining the Dephasing Representation with accurate on-the-fly ab initio electronic structure calculations, including nonadiabatic and spin-orbit couplings.
Finally, the inherent semiclassical approximation was removed in the exact quantum Gaussian Dephasing Representation. Among other examples I will present an ab initio semiclassical dynamics calculation of the time-resolved stimulated emission spectrum of the 54-dimensional azulene and the theoretical justification of the violation of Kasha’s rule of excited-state photochemistry in azulene, using the Multiple Surface Dephasing Representation.