Reactive scattering of a supersonic alkali atom beam: K + Br2, BrCN, SnCl4, PCl3, CCl4, CH3I

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Abstract
Angular distribution measurements of reactive scattering of a supersonic potassium atom beam by a series of molecules are reported with initial kinetic energy (∼ 5 kcal mole-1) above the thermal energy range. The narrow Laval nozzle velocity distribution gives improved resolution over thermal energy measurements. Total reaction cross sections are found to decrease with energy. Differential reaction cross sections for Br2, BrCN and CCl4 show increased forward scattering compared with thermal energies but for CH3I there is no change to within experimental error. The BrCN scattering is compatible with spectator-stripping dynamics, though this limit has not been reached in the Br2 scattering. The SnCl4 differential reaction cross section appears not to be compatible with a single peak in the centre of mass recoil velocity distribution. It is suggested that high and low velocity contributions to the intensity may arise from a long-lived collision complex dissociating by two reaction paths.