Vibrational Energy Transfer from a Homologous Series of Chemically Activated Radicals

Abstract

The relative collisional efficiencies $\beta$ 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 $\beta$ 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, $\text{〈ΔE〉\hspace{0.17em}=\hspace{0.17em}1.3, 2.3, 4.3,}$ 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.