Multiphoton-multiphonon theory of laser-stimulated surface processes

A theoretical model for multiphoton laser-excitation and multiphonon T1 and phase T2 relaxation of molecules adsorbed on a solid surface is developed. The ensemble-averaged excitation number for the infrared-active adspecies is obtained within a Heisenberg-Markovian approximation. The selective nonthermal excitation is sensitive to the mass ratio of the surface atoms and the adspecies, the order of the multiphonon excitation and the duration of the laser pulse.