A discharge-flow study of some fundamental recombination reactions of oxygen atoms in the gaseous phase

Abstract

A chemiluminescence discharge-flow method was used to determine the rate constant k_1,M in the reaction: O(3P) + O₂ + M = O₃ + M for M = O₂, Ar, He, N₂, CO and CO₂ at 295 K and for M = O₂, Ar and CO₂ in the range 196-500 K at pressures in the region of 1-15 torr. The kinetic method developed enabled wall recombination coefficients, in the presence and absence of added reactant oxygen gas, to be determined individually. The use of the 'blank method' at temperatures above 300 K helped solve the discrepancy in rate constants as determined by earlier static (pulse radiolysis, flash photolysis etc.) and flow methods. The allowances for wall recombination depend on the gas phase composition (blank corrections were not made by earlier workers). In addition, in earlier flow experiments, the temperature dependence was determined for a constant mole fraction of O₂ in the presence of a third body. This work shows how an accurate, reliable determination of k1,M is needed. 1) for calculations on catalytic destruction of ozone in the stratosphere. 2) to supply accurate data on theoretical 'computer model' calculations of k_1,M based on classical RRKM theory, and 3) to set up a cheap, reliable, sensitive and alternative experimental technique to expensive and more modern ones.

The results in the range 196-500 k can be written in the form: [diagram]