Surface photochemistry of molecular solids. Dissociative desorption of NO from ClNO by pulsed 193 nm laser radiation

Abstract

The surface photochemistry of 77 K cold films of ClNO has been studied using pulsed 193 nm laser radiation for photolysis and state-resolved probing of desorbed NO by laser-induced fluorescence (LIF). The translational and internal, that is electronic, vibrational and rotational distributions of product NO have been measured and have been used to characterise two distinct desorption channels: laser-induced thermal desorption of residual NO from the solid yields cold NO thermally equilibrated with the surface [12], whereas resonant dissociative desorption of ClNO leads to thermally non-equilibrated hot NO. The non-Maxwellian velocity distributions, Boltzmann-like rotational distributions and the non-inverted vibrational distribution observed for the hot NO indicate that the resonant dissociative desorption of ClNO proceeds by a complex mechanism. Energy disposal into NO is dominated by electronic and vibrational relaxation of the excited parent at the interface.