Resonant short-pulse effects on nuclear motion in the electronic ground state

Abstract

We investigate several approximate treatments of the pulse propagators describing the effects of electronically resonant ultrashort light pulses on the states of molecules in condensed phases, including the classical Franck approximation and a quadratic Hamiltonian treatment. Using a Morse oscillator model of iodine, we examine the effects of the initial form and motion of the pump-induced nuclear density matrix increment on pump-probe signals. We also clarify the conditions of high temperature and short-pulse duration under which the contribution of nuclear dynamics in the electronic ground state to a pump-probe signal will bear a definite sign.