Transfer of Vibrational Energy from Highly Excited Butyl Radical. Part 1. Relative Collision Diameters of Homologous n-Perfluoro Alkane Bath Molecules. Part 2. Structural Effects on the Magnitudes of the Relative Collision Diameters.

摘要

Vibrationally excited n-butyl-2radicals were collisionally deactivated by a homologous series of perfluoro-n-alkane bath molecules, CF4to C8F18,at 298K and 195K. Increments in collision diameter were determined per CF2group. Relative collision diameters referenced to cis-butene-2were measured. Comparison of results at both temperatures indicate that the temperatures indicate that the temperature dependence of collision diameters does not follow the prediction of the 6-12potential. Relative collision diameters for energy transfer were measured at room temperature in the butyl-2system for substituted and cyclic fluorocarbon molecules. Three generalizations are illustrated by the data. (1) Branching of fluoroalkanes causes a decrease of the collision diameter. (2) Cyclization of the fluoroalkane chain decreases the effective size. (3) Introduction of terminal double bonds decreases the size. A simple equivalent sphere model based on the longest end-to-end carbon chain systemizes the relative collision diameters of related molecules. (Modified author abstract)