The influence of the attractive well on near and non-resonant vibrational energy transfer in the gas phase: CO(v = 1) deactivated by methane deuteroisomers

Rate constants for the vibrational deactivation of 12C16O(v = 1) and of 13C18O(v = 1) by CH4 have been measured down to 70 K. For these non-resonant processes there is a flattening of the temperature dependence of the rate constants at the lowest temperatures. The temperature dependence of the rate constants for the near-resonant deactivation of 12C16O(v = 1) by CD3H and CD4 is qualitatively different; below 80 K the rate constants fall off rapidly with temperature. It is considered that this is due to the trapping of the collision partners in the attractive well, while no trapping can occur for the highly exothermic energy transfer processes.