Vibrational relaxation times of oxygen in the pressure range 10–110 atm

Abstract

Measurements of the vibrational relaxation times and sound velocities of oxygen have been carried out at room temperature over the pressure range 10–110 atm. Over this pressure range not only are the effects of vibrational relaxation evident but also of significance are real gas effects. The observed dependence of sound velocity on pressure is in good agreement with theory. Variation of the relaxation frequency with pressure does not exhibit the linear dependence expected on the basis of binary collisions. Extrapolation of the data suggests that in the limit of vanishing pressure, the product p0τv >6(−2) sec·atm. Use of a semiempirical formula combining both the expected high and low pressure dependence of τv suggests in the limit of vanishing pressure that p 0 τ v → 9.76(−2) sec · atm . Both of these are significantly longer than previously determined values.