Mutual neutralization of H+ and D+ with the atomic halide anions Cl-,Br-, and I.

Mutual neutralization (MN) rate constants kMN for the reactions of H+ and D+ with the atomic halide anions Cl-, Br-, and I- were measured using the variable electron and neutral density attachment mass spectrometry technique in a flowing afterglow Langmuir probe apparatus. At 300 K, the rate constants for each reaction studied are on the order of 10-8 cm3 s-1. A trend for the rate constants of the systems in this work, kMNCl-<kMNBr-<kMN(I-), is consistent with prior studies of rare gas cation with atomic halide anion MN. A recent theoretical study involving ab initio quantum mechanical treatment of the H++Cl- and D++Cl- reactions reported rate constants significantly lower than the rates reported here. A previously proposed empirical model that predicts atom-atom kMN as a simple function of the total reaction exothermicity shows good agreement with the newly measured rate constants.