Molecular beam studies of methyl radical reactions with halogen molecules: Product angular and velocity distributions

Abstract

Angular and velocity distributions for the products CH3I from CH3+I2, IBr, and ICl and CH3Br from CH3+Br2 have been measured in a crossed molecular beam apparatus. A thermal (∼1000 °K) methyl beam was obtained by pyrolysis and the halogen beam from a supersonic nozzle source. Center of mass cross sections were derived by applying deconvolution procedures, where necessary, to correct for the resolution of the time-of-flight velocity analysis system and the thermal velocity distributions of the reactant beams. In all four reactions the methyl halide product recoils backward with respect to the incoming methyl radical. Although all reactions release similar fractions (∼0.3) of the total energy into translational motion, the energy distributions of the products from the Br2 and I2 reactions indicate product repulsion, whereas those from the mixed halogen reactions indicate more statistical behavior, as shown by a suprisal analysis.