Radiative Transitions for Molecular Collisions in an Intense Laser Field

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 h bar omega 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(2P3/2) + H2(v = 0) + h bar omega Br(2P1/2) + H2(v = 0). Author)
Reprinted from Faraday Discussions of the Chemical Society, n62 p247-254 1977.