Dissociation of Physisorbed Halomethane Molecules by KrF Excimer Laser Radiation

Abstract

The competitive processes of photolysis and desorption of CF2Cl2, CCl4, CHF2Cl, CHCl3, CH2Cl2, CH2I2, and CH3I halomethane molecules physisorbed on fused silica were experimentally studied. These processes were induced by the absorption of high-intensity UV radiation from a KrF excimer laser by these molecules. It was shown that a common feature in the behavior of all of these compounds is nonlinear dependence of desorption on radiation intensity, typical nonlinearity indices being very high: n = 5–7. One-photon dissociation was carried out in the adsorbed state of CCl4, CH2I2, and CH3I molecules absorbing radiation with a wavelength of 248 nm and in a gas phase. The photofragments are characterized by kinetic energies lower than 0.2 eV. The multiphoton fragmentation of the adsorbed molecules was observed and discussed.