Measurement of rate constants for ion-ion reactions - O+ and N+ with the atomic halide anions Cl-, Br-, and I- at thermal energies

We present 300 K rate constants for the ion-ion reactions of O+ and N+ with the atomic halide anions: Cl-, Br-, and I- measured using a flowing afterglow Langmuir probe apparatus. All six rate constants were >1 x 10(-8) cm(3) s(-1), larger than those typical for atomic ion - atomic ion reactions, approaching the rate constants of more complex ion-ion systems. Evaluation of literature atomic ion - atomic ion rate constants shows variation over orders of magnitude, but limited to below the expected value for a polyatomic ion-ion reaction of the same reduced mass, fitting into an expected physical picture. Unlike for polyatomic systems, estimation of rate constant for atomic ion - atomic ion reaction rates by simple means does not seem effective.