Electronically excited bromine atoms Br(42P½). Part 1.—Primary processes in the photolysis of simple bromides and spin-orbit relaxation of Br(42P½)

Abstract

Electronically excited (4p²P_½) and ground state (4p²P) bromine atoms, resulting from the flash photolysis of a number of simple bromides, have been observed using kinetic spectroscopy in the vacuum ultra-violet. The effect of wavelength on the primary processes has been investigated and has involved the use of vacuum ultra-violet flash photolysis. Br(4²P_½) was observed on photolyzing the molecules HBr, Br₂, CHCl₂Br and CF₃Br but not from CH₃Br, C₂H₅Br and CH₂Br₂. With HBr, the Lyman α transition of the hydrogen atom was also detected. The nature of the primary processes are discussed. The decay of Br(4²P_½) was measured in the photolyses of HBr and CF₃Br. With the latter, the yield of electronically excited atoms on photolysis is sufficiently high for the deactivation by added gases to be determined. The deactivation cross-sections σ² for CF₃Br, HBr and Br₂ were 4.5 × 10^–3, 0.09 and 1.7 Ų, respectively.