Comparison of molecular oxygen and hydrogen halide excitation

3 Comparison of molecular oxygen and hydrogen halide excitation 

collisional relaxation of rotation is fast. One to ten collisions are sufficient for rotation-translation energy transfer. At 1 torr at least one collision per microsecond will occur for both 02 and HC1. In contrast, rotational relaxation by radiation, when allowed, is very slow, of the order of 102 seconds. The absence of 

The importance of vibration-vibration exchange is now apparent in the results of the early experiments on HC1 and on hydroxyl (from H+03 - OHp+02) at pressures above 0.1 torr. These showed vibrational distributions that were nearly Boltzmann, but with shape parameters corresponding to temperatures of several thousand degrees, far greater than the translational temperatures. These distributions were samples taken after rotational relaxation and after the efficient vibration-vibration energy exchange 

A similar exchange has been shown to occur rapidly in the ozone photolysis system40 408, viz. 

Because of this, the 02 population distributions should be considered as the result of (at least) two reactions of similar speeds 

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