Vacuum ultraviolet photoelectron spectroscopy of transient species

The HeI photoelectron spectrum of the SH(X 2II i ) radical produced from the rapid reaction has been recorded. Five bands were observed corresponding to ionization of SH(X 2II i ) to the X 3Σ-, 1Δ, 1Σ+, 3II and 1II states of SH+. Vibrational structure was observed for the first four bands and in each case this was confirmed as arising from SH by recording the corresponding SD spectrum. The vibrational fine structure and band envelopes have been used to estimate the SH+ equilibrium bond lengths in four of the five states. Ionization energies of SH have been estimated using ab initio ΔSCF calculations which included the effects of electron correlation. Similar calculations have also been carried out for the corresponding OH+ states. Good agreement between experiment and theory is obtained. Use of high atomic fluorine partial pressures, relative to hydrogen sulphide, has enabled the first photoelectron spectroscopic observation of sulphur atoms to be made; atomic sulphur was produced as a result of the secondary reaction