Time-Dependent Quantum Wave Packet Dynamics of S + OH Reaction on Its Electronic Ground State

Abstract

Initial state-selected dynamics of the S((3)P) + OH (X(2)Π) → SO (X(3)Σ(-)) + H ((2)S) reaction on its electronic ground potential energy surface (X̃(2)A") is investigated here by a time-dependent wave packet propagation (TDWP) approach. Total reaction probabilities for the three-body rotational angular momentum up to J = 138 are calculated to obtain converged integral reaction cross sections and state-specific rate constants employing the centrifugal sudden (CS) approximation. The convergence of the latter quantities is checked by varying all parameters used in the numerical calculations. The cross section and rate constant results are compared with those available in the literature, calculated with the aid of the quasi-classical trajectory method on the same potential energy surface. Reaction probabilities obtained with the TDWP approach exhibit dense oscillatory structures, implying formation of a metastable quasi-bound complex during the collision process. The effect of rotational and vibrational excitations of reagent OH on the dynamical attributes is also examined. While the rotational excitation of reagent OH decreases the reactivity, its vibrational excitation enhances the same.

State-to-State Dynamics of the Ne + HeH+ (v = 0, j = 0) → NeH+(v′, j′) + He Reaction

“…Such an inhibition of the reactivity by rotational excitation of the reactants has been reported for many other barrierless exothermic processes before. 62,63 As shown in our previous study, 31 the minimum energy path for the reaction corresponds to a collinear or near-collinear approach of the reactants. Rotationally excited reactants disrupt this preferred orientation for the collision and as a result, reactivity decreases when the process is initiated from HeH A comparison between the total reaction probabilities for some selected Js calculated via the QM, SQM and QCT methods is presented in Figure 3.…”

“…This type of behavior has been observed for other barrierless exothermic reactions. 23,[58][59][60][61][62][63] However, in the case of (v 0 , j 0 ) = (0,0), an increasing behavior of the probabilities is noticed in the high energy regime for small Js. For J = 50, P(E) become remarkably smaller and resonances are much broader.…”

“…This behavior of cross sections is similar to other barrierless exothermic reactions. 22,36,[58][59][60][61][62][63] As it is seen in Figure 4, the oscillatory structure of quantum reaction probabilities is greatly reduced in the QM ICS plots due to the partial waves-averaging effect.…”

“…Substantial decrease in the ICSs at low collision energies with vibrational excitation has also been observed for exothermic C+OH reaction. 69 Inhibition of reactivity due to rotational excitation is seen for many exothermic reactions, 59,62,63 which may be related to orientation effect of the reactants. Similarities among the cross sections for different initial rovibrational states in the high energy region is also common for exothermic reactions 59,62,63,69 with no barrier along their collision paths.…”

“…69 Inhibition of reactivity due to rotational excitation is seen for many exothermic reactions, 59,62,63 which may be related to orientation effect of the reactants. Similarities among the cross sections for different initial rovibrational states in the high energy region is also common for exothermic reactions 59,62,63,69 with no barrier along their collision paths. The ICSs for a barrierless exothermic reaction can be calculated by the Langevin capture model, which expresses the ICS for a reaction between an ion and a neutral species as 70,71 σ…”