Primary processes in the 121.6 nm photolysis of gas phase ethyl bromide

Abstract

The vacuum UV photolysis of ethyl bromide at 121.6 nm (235.2 kcal mol −1) has been studied over the pressure range 0.5 – 100 Torr at room temperature using a hydrogen atom resonance lamp. The scavenger effect of the reaction was observed by adding NO gas as a radical scavenger. The pressure effect was also investigated with CF 4 as an additive. The major products of the reaction were CH 4, C 2H 4, C 2H 6, C 2H 2 and CH 3CHBr 2 via a two-channel competition between molecular elimination and the formation of radicals. The decomposition modes in the primary process were 58.7% molecular elimination and 41.3% radical reaction. It was estimated that the portion of hot C 2H 4 molecules produced through the molecular elimination process with more than the threshold energy ( E 0 = 80 kcal (mol −1) for decomposition to C 2H 2 was 25% of the total energy distribution.