Experimental and ab initio study of the infrared spectra of ionic species derived from SF6 and SF4 and trapped in solid neon

When a Ne:SF6 mixture is subjected to Penning ionization and/or photoionization by neon atoms in their first excited states, between 16.6 eV and 16.85 eV, and the products are rapidly frozen at approximately 5 K, the infrared spectrum of the resulting deposit includes prominent absorptions of SF4 and SF5. Other prominent product absorptions are assigned to SF5+ and SF5−, and one absorption is tentatively assigned to SF6−. Similar experiments on a Ne:SF4 sample yield SF4+, SF3+, and SF4−, as well as some F2SO+ and F2⋯SO, derived from F2SO impurity. The spectroscopic identifications of the SFn cations and anions are aided by the results of ab initio calculations. Because the vertical electron detachment energy of SF5− is exceptionally high, this species is stable on unfiltered mercury-arc irradiation of the deposit.