Retardation effects in the dynamics of open molecular systems

Abstract

The non-Markovian version of the quantum master equation (QME) responsible for the time evolution of a reduced density operator is discussed with emphasis on the influence of external field pulses. Different methods to account for the retardation effect in the course of the numerical solution of the QME are reviewed. An application is given for femtosecond optical transitions in molecular systems and the resulting vibrational relaxation processes. The expansion in terms of Laguerre polynomials is introduced as an effective scheme for the numerical description of retarded vibrational energy dissipation. As a result of numerical simulations one can state that retardation effects become more and more pronounced with decreasing duration of the exciting laser pulse. Finally, analytical solutions are presented for non-trivial versions of the non-Markovian QME.