Infra-red emission from shock-heated mixtures of carbon monoxide and neon. Examination of the Landau—Teller model for vibrational relaxation

Abstract

The relaxation times for the fundamental and first overtone emission of CO have been measured for the pure gas and in mixtures with Ne over the temperature range 1520 to 2580 K. The results can be fitted, using the usual formula for mixtures, with the two equations: CO(CO) log₁₀(τ/atm s)= 69.4 ± 3.9(T/K)^–⅓–9.63 ± 0.42, CO(Ne) log₁₀(τ/atm s)= 64.6 ± 9.0(T/K)^–⅓–9.40 ± 0.75, in good agreement with previous estimates.

The relaxation time for the overtone was found to be systematically less by 3 to 10 % than that for the fundamental and the possible causes for this discrepancy have been investigated for several models by computer integration of the rate equations. It was found that the discrepancy could not be explained by any reasonable model which included resonance transfer reactions since these act, even in extreme cases, to maintain a quasi-Boltzmann equilibrium among the vibrational levels. The results indicate that because of this effect it is unlikely that it will be possible to measure separately the rates of Landau–Teller reactions and those for resonance transfer with the present techniques.