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

Observations are presented on theJ-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 theP(20)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 transitionsP(10)-P(34). The data show that the decay times of the variousJstates in the CO200°1 level get progressively longer for increasing or decreasingJvalue centered about the perturbedJ = 19state. 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 = 2changes in collision. The analysis, when compared with the data, indicates that collisions in which by more than two units must also be considered.