Communication: Transfer ionization in a thermal reaction of a cation and anion: Ar~+ with Br- and I-

摘要

We present experimental evidence that reactions of argon cations Ar ~+ with the halogen anions Br~- and I~- do not occur exclusively by mutual neutralization, but also produce the cations Br ~+ or I~+ ions by transfer ionization (TI). The experiments were carried out in flowing-afterglow plasmas at gas temperatures between and 300 and 500 K, and employed a variant of the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The measured TI rate coefficients are 1.9 ± 0.6 × 10~(-9) cm~3 s~(-1) and 1.1±0.30.8 × 10~(-9) cm~3 s~(-1) for the Br- and I- reactions, respectively. We find that the TI rate coefficients decline with temperature as T~(-0.5) to T ~(-1). No indication of TI was found in the reaction with Cl ~-, where it is endoergic.