Is the depletion of ozone by HSO an exothermic process?

Abstract

The Oaussian-2 (02) theoretical procedure, based on ab initio molecular orbital theory, as well as other high level ab initio calculations [QCISD(T) and CCSD(T)/6-311 + +0(3df,2pd, and QCISD(T)/6-31I+0(5d2f,2p)] which avoid the additivity scheme of this theory, are used to estimate the heat of formation of HSO. For this purpose, we propose also, as a further improvement of the standard 02 scheme, to evaluate the residual correlation effects by using the QCISD(TQ) method, which is exact in fifth order rather than the usual QCISD(T) procedure. The heat of formation of HSO at 0 K estimated using different reactive processes is -4.2± 1.3 kcallmol. The most significant consequence is that the depletion of ozone by HSO is predicted to be slightly endothermic rather than exothermic, as it has been concluded in other theoretical studies. We have also found that HSO is more stable than SOH, but the energy gap between both isomers predicted by our calculations is smaller than previous reported values.

Theoretical study of the electronic and hyperfine structures of the HSO and SOH radicals

“…However, after the work of Xantheas and Dunning [10,11] with multireference methods and correlation consistent basis sets of up to quintuple-f quality, it seems well-established that HSO is more stable than SOH. Further theoretical investigations of Espinosa [12], Essefar [13], Wilson [14], Goumri [15], Decker [16], Denis et al [17,18] and Wilson et al [19,20] confirmed the preference of the HSO isomer.…”

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O2

“…[43][44][45] The MG3S basis set fulfils this requirement. It is a basis set 46 identical to 6-3111G(2df) for C and O and to 311G(2p) for H. For the sulfur atom, this basis set stands for the 6-3111G(3d2f) Pople's one.…”

Laser spectroscopy of the 2A′−2A′′ system for the HSO radical

“…Because the reactions (1) and (3) are regarded as an ozone depletion cycle [4,5], a number of theoretical studies [6][7][8] of the HSO radical have been reported so far. In 1978 Schurath et al have observed theà 2 A 0 ÀX 2 A 00 system of HSO by chemiluminescence spectroscopy [9].…”