Infrared laser-induced photolysis of ethylene.

Abstract

The decomposition of ethylene by high-power infrared laser radiation has been studied. The influence of pressure, beam intensity, and irradiation time on the product distribution was investigated. Isotopic mixtures were also irradiated to gain insight into the mechanism and to investigate isotopic selectivity of the process. Changes in mechanism were apparent as the reactant pressure was varied. Evidence is present for a low pressure, collisionless, isotopically-selective multiphoton process. At higher pressures, collisions produce relaxation of vibrational energy and a diffusion-controlled thermal pyrolysis becomes the important process. There is a pressure threshold for a given intensity above which optical breakdown occurs accompanied by visible luminescence and rapid decomposition.