Photoelectron spectra of halides

Abstract

High resolution photoelectron spectra, obtained with He I (584 Å) resonance radiation, are reported for ClF, ClF3, BrF3 and BrF (partial spectrum). In some cases Ne I (736–744 Å) radiation has also been used. Spinorbit and vibrational fine structure is resolved for the ground 2II states of ClF+ and BrF+; values obtained for ClF+ and ζ = 630 cm-1, v′ = 870 cm-1, and for BrF+ ζ = 2600 cm-1, v′ = 750 cm-1. From the vibrational envelope of the X 2∏ states, a bond length change of δr e (-)0·10 Å for ClF+ and BrF+ is estimated. Ab initio SCF-MO calculations for ClF and ClF3 are used to aid in the interpretation of the spectra via Koopmans' theorem. A considerable amount of charge delocalization in the trifluorides is inferred from the photoelectron spectra, and this is borne out by the calculations.