Vibrational relaxation of gaseous CO(v=1) and N2(v=1) from 300 K to liquid temperatures: A comparison with liquid state relaxation

Abstract

The V–V energy transfer rate constants are reported for the deactivation of both CO(v=1) and N2(v=1) by O2 and CH4 in the temperature range 300 to 80 K. The results are obtained by an infrared fluorescence technique. In order to study the relaxation of N2(v=1), a small amount of CO is added to the gas mixture to function both as a pump and a probe. The probability vs temperature curves obtained are approximately parallel for the deactivation of CO(v=1) as compared to that of N2(v=1). This temperature dependence is found to resemble that for the V-T deactivation of CO at low temperatures. This is due to the large mismatch for these V–V energy transfer processes. The rate constants at liquid N2 temperatures are compared with rate constants measured by other researchers for relaxation of the same systems in the liquid phase. The results show that the relaxation rate constants, expressed in terms of cm3 s−1 molecule−1, are approximately equal in the two phases. The implications of this result with respect to the cell and statistical models of vibrational relaxation in liquids is discussed.