An investigation of electron attachment to CHCl2F, CHClF2 and CHF3 using an electron-swarm mass spectrometric technique

Non-thermal energy electron swarm attachment studies of the hydrochlorofluorocarbons CHCl2F and CHClF2 and the hydrofluorocarbon CHF3 have been carried out using an ion-mobility mass spectrometer. Mean electron energies from about 0.05 eV up to about 1.8 eV were covered by using a suitable choice of buffer gases and electric field strengths in the drift chamber of the instrument. Of the three molecules, only CHCl2F and CHClF2 had measurable density normalised electron attachment coefficients over the range of mean electron energies covered. From these coefficients, electron attachment rate constants were determined as a function of mean electron energy. An unfolding technique has been applied to our measurements of the electron attachment rate constants of CHCl2F and CHClF2 to obtain the total electron attachment cross section as a function of electron energy. Uniquely, the mass spectra of the anion products resulting from the electron attachment process and subsequent anion-molecule reactions in a swarm environment were measured with our apparatus, and these are reported. (C) 1997 Elsevier Science B.V.