Theoretical Study for the Ground Electronic State of the Reaction OH + SO → H + SO₂

Abstract

The reaction OH + SO → H + SO2 plays an important role in the combustion of sulfur-containing fuels and the environment. Its reaction profile resembles that of OH + CO → H + CO2, which presents a prototypical reaction with the formation of deep complexes. In this work, a new potential energy surface (PES) for the OH + SO → H + SO2 reaction is developed based on ca. 39 200 data points calculated at the level of the explicitly correlated unrestricted coupled cluster method with single, double, and perturbative triple excitations with the augmented correlation-consistent polarized triple zeta basis set (CCSD­(T)-F12a/AVTZ). The PES is invariant with respect to the permutation of the two identical oxygen atoms, which is guaranteed by the permutation-invariant polynomials as the input layer of the neural network. Using this PES, the quasiclassical trajectory method is employed to study the collision energy transfer between H and SO2 at the experimental translational energy of 59 kcal mol–1. The predicted large integral cross sections for trajectories producing SO2 with high vibrational energy and populations of the SO2 vibrational energy are in good agreement with the recent experimental and theoretical results. Detailed analysis shows that there are two possible mechanisms, a direct mechanism (without passing through HOSO or the HSO2 well) and an indirect one (passing through one or both wells). The latter dominates in producing SO2 with high vibrational energy.

Spectroscopic Characterization of the First and Second Excited States of the HOSO Radical

“…These calculations indicate that the first excited state is a nonplanar structure and has an adiabatic excitation energy of 1.45 eV (855 nm), whereas the second excited state has a planar structure and has an adiabatic excitation energy of 2.91 eV (426 nm). Although the 1 2 A and 2 2 A states exhibit large permanent dipole moments of 2.70 and 1.43 D, previous studies 19,43 indicate that rapid dissociation is possible following electronic excitation, so rotational spectroscopic studies may prove difficult without rapid stabilization of excited state HOSO.…”

“…These dipole moments are significant in magnitude, and rotational spectroscopic studies of these states may be feasible assuming that a sufficient amount of the excited state species can be prepared. However, rapid dissociation is predicted to occur upon UV excitation, , reducing the possibility of stabilization in the excited states.…”

“…Additionally, given the large oscillator strengths of the 2 2 A ← X ̃2A and 3 2 A ← X ̃2A 19 transitions, along with the large absorption cross section and fortuitous spectral overlap at ∼250 nm, the 225−275 nm region may be a good place to begin probing electronic excitation of HOSO. It should also be noted that Qin et al and Trabelsi et al predicted that electronic excitation will most likely result in dissociation along the S−O bond to form SO + OH, 19,43 meaning sophisticated detection methods (e.g., OH laserinduced fluorescence) may be needed in order to detect electronic excitation of HOSO.…”

Data Quality, Data Sampling and Data Fitting: A Tutorial Guide for Constructing Full-dimensional Accurate Potential Energy Surfaces (PESs) of Small Molecular Systems

“…48,146 Practically, the required PIPs under the order of M can be obtained by the software, MAGMA 147 and SINGULAR. 148 Full-dimensional accurate PESs of the following systems have been fitted by the PIP-NN method: F + HCl, 149 H + Li2 → Li + LiH, 150 Si + H2 → SiH + H, 151 N + O2 (doublet, quartet, and sextet states), 152 H + MgH → Mg+H2, 153 O + + H2, 154 S + + H2 → SH + + H, 155 K + H2 → H + KH, 156 H + HBr → H2 + Br, 157 N + + H2 → NH + + H, 158 Au + + H2 → H + AuH + , 159 OH + SO → H + SO2, 102,103 C + H2O → CO + H2/2H, 160 F + H2O → HF + OH, 94,126,161 Cl + H2O → HCl + OH, 84 HCl + OH → Cl + H2O, 162 OH + CO → H + CO2, 163 HOCO -, 164 CO + CO, 132 O + H2O, 126,165 H + HO2, 166 C2H2, 167 HF + HF, 168 KRb + KRb → K2 + Rb2, 169 H + H2S → H2 + SH, 170 NH + + H2 → N + H3 + /NH2 + + H, 171 OH + O2 → H + O3/ HO2 + O, 88 OH + + H2 → H + H2O + , 172 H2 + HF, 173 NH3, 174 H2 + HCl, 124 N2 + HF, 175 N2 + HOC + → N2H + + CO/N2 + HCO, 176 CH2OO, 114 dioxirane, 117 O + C2H2 → H + HCCO/CO + CH2, 177 CO + H2O, 123 C2H2 + Ne, 178,179 OH + H2O → H2O + OH, ...…”

High-Fidelity Potential Energy Surfaces for Gas-Phase and Gas–Surface Scattering Processes from Machine Learning

“…This creates some redundancy but does not affect the fitting accuracy. Since our last review in 2016, this method has been successfully applied to a wide range of reactive systems with up to seven atoms, including KRb + KRb, Be + + H 2 O, OH + SO, OH + O 2 , OH + H 2 O, O + C 2 H 2 , OH + HO 2 , N 2 + HOC + , Cl + CH 4 , F + CH 3 OH, and Cl + CH 3 OH . The latter two cases involve 15 DOFs, with multiple reaction channels and rich dynamics.…”