A model calculation for photo-stimulated desorption of molecules adsorbed on metal surfaces

A model calculation is presented for the photo-stimulated desorption of molecules adsorbed on a metal surface. In the model, the electronic system of the material consists of two energy bands which are described by a tight binding Hamiltonian. The total energy of the electronic system is assumed to give the potential energy for the molecular motion. The time development of the total wavefunction including one coordinate of the molecular center-of-mass and those of electrons is calculated in order to see the relation between the electronic transition by light irradiation and the transition of the state for the molecular motion explicitly. The magnitude of the photodesorption probability calculated for NO/Cu(111) is comparable to that deduced from experimental results.