Systematics of vibrational relaxation

Abstract

A large number of data points for the vibrational relaxation time (pr v in atm sec) of simple systems have been logarithmically plotted vs (T°K)-1/2. It appears that each system is well represented by a straight line, and that most of these straight lines when extended to higher temperatures intersect near the point [prv= 10-8 atm sec, (T°K)-1/2=0.03]. Systems with a small reduced mass μ are exceptions to such a simple convergence, and in an improved scheme, the location of the convergence point is dependent on the reduced mass. Such a presentation has lead to an empirical equation correlating available measurements of vibrational relaxation times: log10(prv) = (5.0×10-4)μ1/2θ5/2[T -1/2-0.015μ1/2]-8.00, where θ is the characteristic temperature of the oscillator in K deg. This equation reproduces the measured times within 50% for systems as diverse as N2, I 2, and O2-H2. In the worst case thus far, O2-Ar near 1000°K, it is off by a factor of 5.