THEORETICAL-STUDIES OF SULFUROUS SPECIES OF IMPORTANCE IN ATMOSPHERICCHEMISTRY .1. CHARACTERIZATION OF THE HSO AND SOH ISOMERS

The molecular structures, relative energies, and vibrational frequenci es of the two stable isomers formed by the addition of (H(S))-S-2 to S O(X3SIGMA-), namely, HSO and SOH, are computed using multiconfiguratio n wave functions and correlation-consistent basis sets of up to quintu ple zeta quality. Contrary to results from previous calculations, the HSO isomer is predicted to be more stable than the SOH isomer by 5.4 k cal/mol. The barrier for the migration of the H atom between the two i somers is computed to be 46.3 kcal/mol. The transition state for the i somerization of the two species lies below the dissociation limit to H (S-2) and SO(X3SIGMA-), which is calculated to be 56.2 kcal/mol above the HSO minimum. The minimum energy paths corresponding to the additio n of H(S-2) to SO(X3SIGMA-) to form HSO and SOH are also computed; a b arrier of 2.4 kcal/mol is predicted for the addition of hydrogen to th e oxygen side of SO. Finally, upper limits for DELTAH(f)-degrees-298 f or HSO and SOH are estimated at -6.1 +/- 1.3 and -0.7 +/- 1.3 kcal/mol , respectively. The latter implies that HSO can be involved in a catal ytic cycle that depletes ozone in the atmosphere.