A microscopic model for electronic quenching in the photodesorption of NO from NiO(100) is developed. The quenching is caused by the interaction of the excited adsorbate-substrate complex with electron hole pairs (O 2p-->Ni 3d states) in the surface. The electron hole pairs are described as a bath of two level systems which are characterized by an excitation energy and a dipole charge. The parameters are connected to estimates from photoemission spectroscopy and configuration interaction calculations. Due to the localized electronic structure of NiO a direct optical excitation mechanism can be assumed, and a reliable potential energy surface for the excited state is available. Thus a treatment of all steps in the photodesorption event from first principles becomes possible for the first time. The surrogate Hamiltonian method, which allows one to monitor convergence, is employed to calculate the desorption dynamics. Desorption probabilities of the right order of magnitude and velocities in the experimentally observed range are obtained. (C) 2003 American Institute of Physics.