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 hydrochlor ofluorocarbons CHCl2F and CHClF2 and the hydrofluorocarbon CHF3 have b een 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 a nd CHClF2 had measurable density normalised electron attachment coeffi cients over the range of mean electron energies covered. From these co efficients, electron attachment rate constants were determined as a fu nction of mean electron energy. An unfolding technique has been applie d to our measurements of the electron attachment rate constants of CHC l2F and CHClF2 to obtain the total electron attachment cross section a s a function of electron energy. Uniquely, the mass spectra of the ani on products resulting from the electron attachment process and subsequ ent anion-molecule reactions in a swarm environment were measured with our apparatus, and these are reported. (C) 1997 Elsevier Science B.V.