Stochastic Trajectory Simulations of Vibrational Energy Flow at Surfaces.

Stochastic trajectory techniques have been developed to examine vibrational motion at crystal surfaces. Introduction of quantum fluctuation-dissipation relations allows extension of the method to low temperatures. Inclusion of supplementary frictional and fluctuating forces can account for coupling of vibrations to electron-hole pairs in metals. Addition of an oscillatory external force that drives the dipole moment of the system emulates resonant or non-resonant infrared excitation. Applications of the method to adsorbate vibrational lifetimes and infrared lineshapes are described. The feasibility of achieving bond- selective chemistry at surfaces by resonant infrared excitation is examined.