Classical stochastic model of laser-stimulated surface processes and the selective nature of laser excitation via multiphonon couplings

The dynamical behavior of laser-stimulated surface processes (LSSP) is studied by the generalized Langevin equation via the memory effects of the damping kernel, the dephasing kernel and mode-mode interactions. The temperature-dependent averaged energy absorption rate (which characterizes the line shape) is calculated by solving the Laplace-Fourier transform of the velocity correlation function. The features of the response function and its overall line broadening are discussed in terms of Markovian processes. The nature of LSSP and laser-selective effects are discussed in terms of the multiphonon coupling strength and the related “internal resonant” condition. It is shown that laser-selective bond breaking is possible for a slow intramolecular vibrational relaxation rate which is governed by a high-order multiphonon process or a far off “internal resonance”.