Mutual Neutralization of Atomic Rare-Gas Cations (Ne+, Ar+, Kr+, Xe+) with Atomic Halide Anions (Cl-, Br-, I-).

摘要

We report thermal rate coefficients for 12 reactions of rare gas cations (Ne+, Ar+, Kr+, Xe+) with halide anions (Cl , Br , I ), comprising both mutual neutralization (MN) and transfer ionization. No rate coefficients have been previously reported for these reactions; however, the development of the Variable Electron and Neutral Density Attachment Mass Spectrometry technique makes it possible to measure the difference of the rate coefficients for pairs of parallel reactions in a Flowing Afterglow-Langmuir Probe apparatus. Measurements of 18 such combinations of competing reaction pairs yield an over-determined data set from which a consistent set of rate coefficients of the 12 MN reactions can be deduced. Unlike rate coefficients of MN reactions involving at least one polyatomic ion, which vary by at most a factor of 3, those of the atom-atom reactions vary by at least a factor 60 depending on the species. It is found that the rate coefficients involving light rare-gas ions are larger than those for the heavier rare-gas ions, but the opposite trend is observed in the progression from Cl to I . The largest rate coefficient is 6.5 10 8 cm3 s 1 for Ne+ with I . Rate coefficients for Ar+, Kr+, and Xe+ reacting with Br2 are also reported.