Vibrational relaxation in polyatomic molecules: SF6

Abstract

Vibrational relaxation in mixtures of 5%, 10%, and 25% SF6 in Ar has been studied behind incident shock waves over the temperature range 450–1050 K by time-resolved measurement of postshock density gradients using a laser beam deflection technique. Short extrapolation of the results obtained yields excellent agreement with ultrasonic data in the range 200–420 K. Contrary to original reports, results from infrared fluorescence and double resonance measurements at 300 K are shown to be in disagreement with the ultrasonic data. A discussion of relaxation behavior in polyatomic molecules under differing conditions of departure from equilibrium shows that such a discrepancy is to be expected in general.