Mutual neutralization of He(+) with the anions Cl(-), Br(-), I(-), and SF6 (.).

Abstract

Mutual neutralization (MN) rate coefficients kMN for He(+) with the anions Cl(-), Br(-), I(-), and SF6 (-) are reported from 300 to 500 K. The measured rate coefficients may contain a contribution from transfer ionization, i.e., double ionization of the anion. The large rate coefficient for He(+) + SF6 (-) (2.4 × 10(-7) cm(3) s(-1) at 300 K) is consistent with earlier polyatomic MN results found to have a reduced mass dependence of μ(-1/2). Neutralization of He(+) by the atomic halides follows the trend observed earlier for Ne(+), Ar(+), Kr(+), and Xe(+) neutralized by atomic halides, kMN (Cl(-)) < kMN (Br(-)) < kMN (I(-)). Only an upper limit could be measured for the neutralization of He(+) by Cl(-). Predictions of the rate coefficients from a previously proposed simple model of atomic-atomic MN results are consistent with the present He(+)-halide rate coefficients. The temperature dependences are modestly negative for Br(-) and I(-), while that for SF6 (-) is small or negligible.