Pump/probe spectroscopy of NaI in rare gas environments: A statistical description

A theoretical study of the femtosecond spectroscopy of the NaI predissociation process under high-pressure conditions is presented. We employ a statistical model to mimic the pressure dependence of pump/probe signals for different rare gases. The model uses an ensemble of trajectories to approximate the quantum dynamics of the wave packet, which is prepared by ultrashort pulse excitation. Predissociation is treated within the Landau-Zener model for curve crossing. Collisions are modeled as instantaneous events assuming hard sphere scattering. The collision probability is calculated statistically so that no adjustable parameter has to be introduced. The results show how coherent wave packet motion is influenced by scattering processes and how this is reflected in femtosecond pump/probe signals.