Vibrational energy transfer between isotopes of CO and isotopes of CO2 in the gas phase and in liquid Kr solution

Abstract

Rate constants are presented for (VV) energy transfer between CO(ν=1) and CO2(0001) in the gas phase down to 115 K and in liquid Kr solution at 118 and 130 K. Four isotopically substituted systems were investigated for which the energy mismatches varied between 104 and 306 cm−1. The gas and liquid phase data show several systematic effects with changing energy mismatch. In particular it was found that the ratio of the liquid and gas phase rate constants at the same temperature, kL/kG, increased with decreasing energy mismatch. This is not predicted by current theories of liquid phase energy transfer and is in contrast to previous work using liquid Kr as the solvent.

Gas-Phase Reactions and Energy Transfer at Very Low Temperatures

“…The data of Wilson et al (81) show a small but significant increase the rate constants for V-V exchange at their lowest temperatures, especially for the systems where A~ is relatively large. It seems likely that this reflects the influence of the permanent intermolecular attraction: For CO-CO2, e/kB = 145 K. Clearly, it would be interesting to study such effects by making measurements at still lower temperatures, but this is unlikely to be possible using cryogenic cooling.…”

“…They use cryogenic cooling and therefore the temperatures of their experiments are limited. Using a frequency-doubled CO2 laser to excite CO and infrared fluorescence to observe how the concentration of CO(v = 1) then decays, they have obtained rate constants for the exchange of vibrational energy between ~2C160 and 15N 2 down to 45 K (80a,b) and between isotopomers of CO and CO2 down to 115 (81). The results, which are shown in Figure 4, confirm a number features that are by now well established in regard to V-V energy exchange between simple molecules in the gas phase.…”