Mode-specific quantum dynamics study of OH + H2S → H2O + SH reaction

Abstract

The hydrogen abstraction reaction from H2S by OH is of key importance in understanding of the causes of acid rain, air pollution, and climate change. In this work, the reaction OH+H2S → H2O+SH is investigated on a recently developed ab initio-based globally accurate potential energy surface by the time-dependent wave packet approach under a reduced-dimensional model. This reaction behaves like a barrier-less reaction at low collision energies and like an activated reaction with a well-defined barrier at high collision energies. Exciting either the symmetric or antisymmetric stretching mode of the molecule H2S enhances the reactivity more than exciting the bending mode, which is rationalized by the coupling strength of each normal mode with the reaction coordinate. In addition, the modespecific rate constant shows a remarkable non-Arrhenius temperature dependence.

Theoretical Insights into the Dynamics of Gas-Phase Bimolecular Reactions with Submerged Barriers

“…We note that mode specificity has also been found in other reactions with submerged barriers, including the neutral OH + H 2 S → H 2 O + SH 122,123 and OH + CO → H + CO 2 reactions 124,125…”

“…We note that mode specificity has also been found in other reactions with submerged barriers, including the neutral OH + H 2 S → H 2 O + SH , and OH + CO → H + CO 2 reactions , and ion–molecule OH + + H 2 → H + H 2 O + , H 2 + NH 2 – → H – + NH 3 , , and H 2 + NH 2 + → H + NH 3 + reactions …”

Vibrational Mode-Specific Dynamics of the OH + C2H6 Reaction

“…Seeing this unexpected finding, it is important to note that we did not find similar violation of the Polanyi rules for the similarly early-barrier F + C 2 H 6 reaction . However, we also note that violation of these rules was reported for several other early-barrier systems such as F + H 2 O, HCl + OH, and OH + H 2 S. – …”

Kinetic and dynamic studies of the NH2+ + H2 reaction on a high-level ab initio potential energy surface

“…These dynamical features are also found in other barrierless reactions, such as OH + H 2 S and OH + HO 2 reactions. 65,66…”

“…These dynamical features are also found in other barrierless reactions, such as OH + H 2 S and OH + HO 2 reactions. 65,66 In addition, one can see that exciting the symmetric stretching mode (v 1 ) is always more efficient than exciting the asymmetric stretching mode (v 3 ) of NH 2 + . Considering that the ab initio frequency of 3511 cm À1 for fundamental excitation of v 1 is only 255 cm À1 higher than that of 3256 cm À1 for v 3 (see Table 3), the larger efficiency of the v 1 stretching mode than the v 3 stretching mode is intriguing.…”