The sound absorption and velocity of NO gas at 293°K was measured from f/p=5×104 to 107 cps/atmos using an ultrasonic pulse method. A maximum of the absorption at 4×105 cps/atmos is ascribed to the relaxation of the oscillational degree of freedom. (τosc=4×10—7 sec at 1 atmos.) According to the absorption at high f/p values, τspin≈4τrot (=2.5·10—9 sec at 1 atmos) seems probable. The result is compared to the corresponding data of O2 and N2.
The vibrational relaxation times of several simple substances in the gaseous and liquid state are compared with values predicted by a simple cell theory of the liquid. Apart from some scatter of the experimental data, satisfactory agreement is found with the theoretical predictions.
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