Quantum-classical correspondence in the O(P-3) plus HCl and Cl(P-2) plus OH reactions for total angular momentum J=0

A method for carrying out quasiclassical trajectory (QCT) calculations of A + BC(upsilon ,j) reactive collisions for the special case of the total ang ular momentum J = 0 is described. Since quantum reactive scattering calcula tions involving heavier atoms are not straightforward for the J>0 case, thi s method is useful to establish the extent to which classical mechanics is applicable to a particular reaction. The method is tested by comparing the results of trajectory calculations for the J = 0 case with analogous quantu m-mechanical (QM) calculations for the O(P-3) + HCl reaction and the revers e reaction Cl(P-2) + OH. The S4 potential surface, which is based on MRCI+Q /cc-pVTZ energies scaled by the scaled external correlation method [B. Rama chandran et al., J. Chem. Phys. 111, 3862 (1999)], is used for these calcul ations. The QCT and QM cumulative reaction probabilities are found to be in good agreement, especially for the Cl + OH reaction. The agreement between the two types of state-resolved reaction probabilities is less striking bu t improves considerably as the initial diatomic rotational quantum number j increases. A comparison is also made between the exact and J-shifted QCT t hermal rate coefficients. These are found to be in excellent agreement, whi ch is in keeping with similar agreement observed in the case of the quantum -mechanical exact and J-shifted thermal rate coefficients. (C) 2001 America n Institute of Physics.