O 2 Vibration Relaxation in Oxygen-Argon Mixtures

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Abstract
This paper and the one following [M. Camac and A. Vaughan, J. Chem. Phys. 34, 459 (1961)] discuss the use of a new experi-mental technique for the determination of O2 vibration and dissociation rates. The concentration of O2 in the ground vibrational state can be inferred from measurements of ultraviolet light transmission at 1470 A. O2 has a strong continuous absorption band in this vacuum ultraviolet region. The vibrational relaxation rate of O2 in shock-heated O2-Ar mixtures was obtained from 1200 °K to 7000 °K. For Ar-O2 collisions, the measured relaxation time t, can be fit by the Landau-Teller theory [L. Landau and E. Teller, Physik. Z. Sowjetunion 10, 34 (1936)] 1/τv = nC1T1/6[1−exp(−2228T)]exp(−(C/T)1/3), where n is the number of particles/cc and T is the temperature in °K. C1 = 1.2×10−7 cc/particle∼sec-(K)1/6 and C = 1.04×107 (±30%)°K. The observed vibrational relaxation time for O2-O2 collisions is 5.0±0.5 times faster than that for O2-Ar collisions. The experimental results are compared to the theoretical predictions of Schwartz and Herzfeld [R. N. Schwartz, Z. I. Slawsky, and K. F. Herzfeld, J. Chem. Phys. 20, 1591 (1952); R. N. Schwartz and K. F. Herzfeld, ibid. 22, 767 (1954)]. At the lower temperatures, the O2-O2 rates given by Blackman [V. H. Blackman, J. Fluid Mech. 1, 61 (1956)] have a different temperature dependence than the O2-Ar rates obtained in this experiment.

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