Partial dissociative ionization ofSF6by electron impact using an ejected electron-ion coincidence technique

Abstract

The relative differential partial ionization cross sections for the production of ionic fragments of ${\mathrm{SF}}_{6}$ molecule under impact of 10--20 keV electrons have been measured using an ejected electron-produced ion coincidence technique in a crossed beam apparatus with a time-of-flight analysis of the ions. The detection angle of the ejected electrons of nondiscriminated energies was kept at 90\ifmmode^\circ\else\textdegree\fi{} with respect to the incident electron-beam direction. The 14 ionic fragments: ${\mathrm{SF}}_{5}^{+},$ ${\mathrm{SF}}_{4}^{+},$ ${\mathrm{SF}}_{3}^{+},$ ${\mathrm{SF}}_{2}^{+},$ ${\mathrm{SF}}^{+},$ ${\mathrm{S}}^{+},$ ${\mathrm{F}}^{+},$ ${\mathrm{SF}}_{4}^{2+},$ ${\mathrm{SF}}_{3}^{2+},$ ${\mathrm{SF}}_{2}^{2+},$ ${\mathrm{S}}^{2+},$ ${\mathrm{F}}^{2+},$ ${\mathrm{SF}}_{3}^{3+},$ and ${\mathrm{S}}^{3+}$ resulting from the dissociative ionization of the ${\mathrm{SF}}_{6}$ molecule were identified and their relative production cross sections have been measured. The branching ratios of 8 ionic fragments ${\mathrm{SF}}_{m}^{n+}$ $(m=1$ to 5 and $n=1$ to 3) as a function of impact energy have been determined. These ratios are found to have an almost a constant value over the considered impact energy range within the experimental uncertainty of the measurements. For the investigated impact energies, no previous data or theoretical calculations exist for a direct comparison with the present results.