J-dependence of rotational relaxation in the CO200°1 vibrational level

Observations are presented on the -dependence of rotational relaxation in the CO200°1 vibrational level for mixtures of CO2, He, and N2. The experiment consists of injecting a saturating ∼2-ns pulse at the line in the 10.4-μ CO2band into a low-pressure CO2-laser amplifier while simultaneously monitoring the transient gain response of an overlapping weak probe beam in the 9.4-μ band restricted to operate on any of the transitions - . The data show that the decay times of the various states in the CO200°1 level get progressively longer for increasing or decreasing value centered about the perturbed state. Such behavior may be expected to have a significant effect on the efficiency of energy extraction and pulse shapes in CO2amplifiers for nanosecond and, especially, subnanosecond laser pulses. An analysis using a coupled set of rate equations to describe the rotational level populations is presented in which consideration is given only to changes in collision. The analysis, when compared with the data, indicates that collisions in which changes by more than two units must also be considered.