Ion–Molecule Reaction Studies from 300° to 600°K in a Temperature-Controlled Flowing Afterglow System

Abstract

The flowing afterglow technique for ion‐neutral reaction rate constant studies has been modified to cover a range of gas temperature from 82° to 600°K. The experimental apparatus is described and rate constants for six reactions between 300° and 600°K are reported. The reaction of He⁺ with N₂ is found to have a rate constant 1.2 × 10⁻⁹ cm/³sec, independent of temperature in this range. The reaction of O⁺ with CO₂ has a rate constant 1.1 × 10⁻⁹ cm³/sec at 300°K, decreasing slightly to 8 × 10⁻¹⁰ cm³/sec at 600°K. The reaction of N⁺ with O₂ appears to have a rate constant 6 × 10⁻¹⁰ cm³/sec throughout this temperature range. The rate constant for charge transfer of N₂⁺ with O₂ is measured to be 4.7 × 10⁻¹¹ cm³/sec at 300°K, decreasing to about 2 × 10⁻¹¹ cm³/sec at 500°K. The rate constant for the reaction of O⁺ with O₂ decreases from 2 to 1.3 × 10⁻¹¹ cm³/sec, and the rate constant for O⁺ + N₂ decreases from 1.2 × 10⁻¹² cm³/sec to about 6 × 10⁻¹³ cm³/sec between 300° and 600°K.