Preferred transition-state geometry in the reaction of fluorine atoms with iodomethane molecules

Abstract

Reactive scattering of F atoms with CH₃l molecules has been studied at an initial translational energy E≈ 34 kJ mol^–1, using a supersonic beam of F atoms seeded in He buffer gas generated by a high-pressure microwave discharge source. The centre-of-mass angular distribution is represented by the Halpern–Strutinski function with a small constant term and a backward peak which is lower than the forward peak by a factor of ca. 0.75. The angular distribution of reactive scattering obtained from these measurements and the angular distribution previously determined by Farrar and Lee at lower initial translational energy E≈ 11 kJ mol^–1 are both consistent with the microcanonical theory for dissociation of an F–l–CH₃ complex via a bent transition state with a preferred interbond angle β≈ 140°.