Vibrational Energy Transfer from a Homologous Series of Chemically Activated Radicals

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Abstract
The relative collisional efficiencies β of several inert bath molecules for the collisional deactivation of a homologous series of highly vibrationally excited species have been measured. The inert gases were H2, and N2 CH4, and CF4, The excited species were 2-butyl, 2-methyl-2-butyl,2-pentyl, 2-hexyl, and 2-octyl radicals. The relative efficiency of a particular bath gas was roughly constant for all members of the series. This finding is discussed and compared with theoretical results on a stochastic model. The approximate values of β are: 0.22, 0.53, 0.78, and 1.0 for H2, N2, CH4, and CF4, respectively. These correspond to average values of the mean energy decrement per collision, 〈ΔE〉 = 1.3, 2.3, 4.3, and >9 kcal mole−1, respectively, for a stepladder model of transition probabilities, and to somewhat larger average values for an exponential distribution of the sizes of energy decrements.