Two channel competitive photodecomposition reaction of gaseous bromoethane at 193.1 nm

Abstract

The vacuum ultraviolet photolysis of gas phase bromoethane at 193.1 nm (6.42 eV) was studied over the pressure range of 1.1–303.2 Torr at room temperature using a carbon atom lamp. The pressure effect with and without inert gas, i.e., He or N2, was investigated. A scavenger effect of the reaction was also observed by adding NO as a radical scavenger. The principal reaction products were C2H6, C2H4, 1,1-C2H4Br2, and n-C4H10. The quantum yields of C2H4 and C2H6 were found to increase slightly with the reactant pressure. When the pressure of He or N2 was varied at a constant pressure of C2H5Br, however, the quantum yields of C2H4 and C2H6 were found to be pressure independent. Addition of NO completely suppressed the formation of C2H6, C2H4Br2, and C4H10, and partially reduced that of C2H4. These results were interpreted in terms of two channel competition between the molecular elimination and the formation of radicals. Two different decomposition modes were 82% radical reaction and 18% molecular elimination.