Radiative transitions for molecular collisions in an intense laser field

Abstract

Quantum mechanical and semiclassical approaches are discussed for the study of molecular collisions in an intense laser field. Both a coherent state and Fock state representation of the photon field are investigated. The collision dynamics is described in terms of transitions between two electronic-field potential energy surfaces, where each surface depends on the field-free adiabatic surfaces and electric dipole transition matrix elements as functions of nuclear coordinates. The electronic-field surfaces exhibit avoided crossings (on the real axis) due to the radiative coupling at the resonance nuclear configurations, and other parts of these surfaces are similar to the field-free adiabatic surfaces with one of them shifted by ħω for single photon processes. Metastable states, formed at some collision energies, are conjectured to occur in the field, although absent from the field-free case. From a spectroscopic point of view, changes in energy spectra are expected from those of the individual collision-free species. Numerical results are presented for the collinear collision process Br(²P_3/2)+ H₂(v= 0)+ħω→ Br(²P_1/2)+ H₂(v= 0).