Photoprocesses induced by short-wavelength excimer laser radiation in adsorbed halomethane molecules

Photolysis and desorption induced by ArF and KrCl laser irradiation of CH₂I₂, CH₃I, CCl₄, CHCl₃, CH₂Cl₂, CF₂Cl₂, and CHF₂Cl molecules adsorbed on fused silica were studied. One-photon fragmentation, as well as nonlinear dissociation and desorption processes, were observed. It was found that three-step fragmentation is a widespread phenomenon for molecules that experience resonant absorption of laser radiation. To explain the phenomenon, a mechanism based on stimulated emission was proposed. The nonlinear character of desorption is associated with redistribution of absorbed energy in adsorbed molecules and its transfer to the substrate.