Ionisation of hydrogen sulphide, selenide and telluride by electron impact

Abstract

Ionisation efficiency curves are reported for H₂S⁺, HS⁺, H₂Se⁺, H₂Te⁺ and HTe⁺. The HSe—H and HTe—H bond dissociation energies have been found to be 3.9 ± 0.2 and 2.9 ± 0.2 eV respectively. There seems to be need to redetermine the heat of formation of hydrogen selenide. Evidence is presented for the formation of vibrationally excited ions which, if confirmed, implies that the ionisation of H₂S, H₂Se and H₂Te by electron impact does not follow the Frank-Condon principle.