A CLASSICAL-ANALYSIS OF PHOTODESORPTION BY RESONANT IR-LASER ADSORBATE COUPLING

Photodesorption induced by IR-laser resonant excitation of an internal vibrational mode of physisorbed molecules is investigated in terms of a simple model, which only considers a non-dissipative energy transfer between the excited intramolccular vibration and the molecule-surface van der Waals bond. Classical simulations are performed for CH3P adsorbed on NaCl and Poincare maps are used to clarity details of the microscopic process responsible for desorption and to identify conditions where the non-exponential time decay to the adsorbate coverage is expected. Photodesorption rates extracted from the classical simulations differ significantly from those obtained using a quantum-mechanical perturbation approach.