The photolysis of halomethanes adsorbed on a transparent substrate by UV excimer lasers has been studied using mass spectrometry of desorbed species. The cubic dependence of photodissociation yield versus laser fluence was discovered. The three-photon dissociation (3PD) mechanism based on molecule transfer to a repulsive electronic state by means of two-photon absorption followed by laser-stimulated photon emission has been proposed. The role of molecular energy relaxation in resonance-enhancement of these processes is discussed. (c) 2008 Published by Elsevier B. V.