Ion appearance energies at electron-impact dissociative ionization of sulfur hexafluoride molecule and its fragments

Theoretical analysis of appearance energies for SFk+ (k = 0-n) ion fragments of SF6 molecule as well as F+ and F-2(+) ions at electron-impact dissociative ionization of SFn (n = 1-6) molecules is presented. Theoretical methods of GAMESS software package were used to calculate the total energies of neutral and charged molecular and atomic fragments. The dissociative ionization process is concluded to occur via repulsive highly-excited electronic states of the SF6 molecule and its fragments, due to which the observed appearance energies exceed the theoretical values. The electron binding energies on the molecular orbitals in the SF6 molecule are compared with the ion fragment appearance energies.