Direct Observation of Electron Disappearance in Pulse Irradiated Fluorocarbon Gases

Abstract

A microwave conductivity detector has been used to follow electron disappearance in pulse irradiated fluorocarbon gases. A discussion of the application of the method to compounds of widely differing electron attachment rate constants and a number of experimental details is given. Eleven simple fluorocarbons, CH2Cl2, and SF6 were studied. Because (except for SF6) these compounds were relatively unreactive, considerable effort was expended upon purification. In many cases the rate of electron attachment found for the purified sample was orders of magnitude less than for the unpurified one. In the homologous series from CF4 to n-C4F10 only the latter was found to attach electrons at an appreciable rate (k = 9.6 × 10−12cm3molecule−1·sec−1). Significantly, CF4 and C2F6 were found to have rate constants < 10−16 cm3 molecule−1·sec−1. The attachment rates of the compounds CH2F2, CHF3, CClF3, and CH3CF3 are all comparable; those of the last three are nearly identical (4 − 5 × 10−14 cm3 molecule−1·sec−1) suggesting the involvement of the CF3 group. The electron attachment rate constant for SF6 was determined to be 2.2 × 10−7 cm3 molecule−1·sec−1.