			15min:

HS-H BOND DISSOCIATION ENERGY DETERMINATION BY THRESHOLD ION-PAIR PRODUCTION SPECTROSCOPY (TIPPS).

X. K. HU, R. C. SHIELL, Q. J. HU AND J. W. HEPBURN, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.

The first single photon threshlod ion-pair production spectrum (TIPPS) of a polyatomic molecule, H₂S, was recorded by monitoring H⁺ ion generated from the dissociation process H₂S \to HS^- + H⁺. Its ion-pair threshold was determined to be IPP = 122458 \pm 3 cm^-1. As a result, the bond dissociation energy (D(HS-H) = 31451 \pm 4 cm^-1) could be calcula ted from D(HS-H) = IPP - IP(H) + EA(HS), by knowing the ionization potential of the hydrogen atom (IP(H) = 109678.772 cm^-1) and the electron affinity of the HS radical (EA(HS) = 18672 \pm 2 cm^-1).