Vibrational Relaxation of Carbon Monoxide in the Shock Tube

Abstract

The rate of approach to vibrational equilibrium of suddenly heated CO has been studied using a shock tube and interferometer in the temperature range 2200–4900° K. Care was taken to ensure purity of the gas, so that the effect of impurities could be considered negligible. The measured relaxation times, which ranged nearly exponentially from 50 μsec at 2200° to 2 μsec at 4900°, agree fairly well with the results of Windsor et al., who covered the range 1400°—3000° using a somewhat different method. Both sets of measurements show satisfactory agreement with Landau‐Teller theory as refined by Herzfeld et al. Separate experiments were performed with CO to which was added about one percent of H₂, N₂, O₂, CO₂, and H₂O, one at a time. CO₂ produced a slight reduction and H₂O a very marked reduction in the relaxation time; the others produced no observable effect.