Rate measurements for the reaction of H-atoms with the xenon and krypton fluoride molecules.

Abstract

Elementary strongly exothermic reactions of H-atoms with the F 2, KrF 2, XeF 2, XeF 4, XeF 6 molecules useful for chemical lasers have been investigated by mass-spectrometric probing of the diffusion cloud in flow [1] . Some ionisation and appearance potentials were defined [2] from experimental ionization efficiency curves. Arrhenius expressions were obtained for the rate constants between 298–505 K. They correspond to an activation energy of 8.9± 0.6; 11.3±0.2; 21.8±2; 22.6±5; 28.5±3.8 kj/mol for the H + F 2, KrF 2, XeF 2, XeF 4, XeF 6 reactions respectively, with the preexponential factor near 10 −10cc/molec-c for all rate constants. It was established that HF product of the H+F 2 “model” reaction is excited up to 8-th vibrational level while such one of the H+ KrF 2 reaction is not vibrationally excited. Thus a second product of H+KrF 2 reaction may be eximer KrF(B 2Σ) with the energy excitation 481.3 kJ/mol which corresponds to sum of the reaction heat and activation energy.