Vibrational relaxation of CO2 (1Â 20Â 1) by argon

We present experimental measurements of the vibrational relaxation of CO2 (1 20 1) by argon, at ambient temperature (295 ± 2 K). The CO2 molecules were directly excited to the (1 20 1, J = 14) ro-vibrational state by a tunable laser radiation at ∼2 μm. Time-resolved infrared fluorescence technique was used to study the collisional relaxation process. The bimolecular deactivation rate constant of CO2 (1 20 1) by argon was found to be (825 ± 43 Torr−1 s−1) while the self-deactivation by CO2 (0 00 0) was determined to be (3357 ± 135 Torr−1 s−1). The radiative life-time of the vibrational combination band (1 20 1), τ[CO2 (1 20 1)], was found to be (5.55 ± 0.27) μs. Modern angular momentum theory was used to explain values of the deactivation rate measured. It is concluded that the presence of the (0 80 0) state acts like an angular momentum sink leading to a fast deactivation rate of the CO2 (1 20 1) by argon.