Gas phase photolysis of 1-butene at 123.7 nm (10.0 eV)

Abstract

The photolysis of 1-butene was carried out in a static system using the krypton resonance line at 123.7 nm (10.0 eV) at pressures in the range 15–500 Torr (2–66.5 kPa). The major products observed were ethylene, acetylene, 1,3-butadiene, allene, n-butane and propylene. Identification of the radical species was made by the use of scavengers such as oxygen and H 2S. Evidence is presented for the occurrence of nine primary processes to which quantum yields have been ascribed. The main processes are fragmentation giving C 3H 5 radicals with a yield φ of 0.29 and the formation of C 4H 6 hydrocarbons with a yield φ of 0.23. A hydrogen atom mechanism, involving the occurrence of hot hydrogen atoms that have an excess energy as high as 0.6 eV, was proposed to account for the pressure dependence of propylene. Dissociation of excited radicals contributes to the formation of ethylene.