Theory of laser-stimulated surface processes. 1: General formulation for the multiphone relaxation of a vibrationally excited adatom

A general expression is obtained for the rate of energy transfer from an adatom-surface bond in an excited vibrational state due to IR laser irradiation to vibrational modes of the solid. The rate is seen to involve time Fourier transforms of powers of a correlation function for the displacement of different lattice particles at different times, reciprocal-space Fourier components of a suitably chosen pair potential between the adatom and each lattice atom and a weight factor associated with the laser-excited state of the adatom-surface bond. This "factorization' of the energy transfer rate into components depending on the properties of the laser, those of the adatom-surface bond and those of the solid provides a simple physical picture of the relaxation process within a rigorous framework and strongly suggests many points of departure towards more phenomenological approaches to laser-stimulated surface processes.