Time-Dependent Quantum Wave Packet Study of the Si + OH → SiO + H Reaction: Cross Sections and Rate Constants
Résumé
The dynamics of the Si(3P)+OH(X2Π) → SiO(X1Σ+)+H(2S) reaction is investigated by means of the time-dependent wave packet (TDWP) approach using an ab initio potential energy surface recently developed by Dayou et al. (J. Chem. Phys. 2013 ,139, 204305) for the ground X2A' electronic state. Total reaction probabilities have been calculated for the first fifteen rotational states j = 0-14 of OH(v = 0, j) at a total angular momentum J = 0 up to a collision energy of 1 eV. Integral cross-sections and state-selected rate constants for the temperature range 10-500 K were obtained within the J-shifting approximation. The reaction probabilities display highly oscillatory structures indicating the contribution of long-lived quasibound states supported by the deep SiOH/HSiO wells. The cross sections behave with collision energies as expected for a barrierless reaction and are slightly sensitive to the initial rotational excitation of OH. The thermal rate constants show a marked temperature dependence below 200 K with a maximum value around 15 K. The TDWP results globally agree with the results of earlier quasi-classical trajectory (QCT) calculations carried out by Rivero-Santamaria et al. (Chem. Phys. Lett. 2014, 610-611, 335-340) with the same potential energy surface. In particular, the thermal rate constants display a similar temperature dependence, with TDWP values smaller than the QCT ones over the whole temperature range.