Exact quantum 3D cross sections for the Ne+H2+→NeH++H reaction by the hyperspherical method.: Comparison with approximate quantum mechanical and classical results

Exact, fully converged three-dimensional quantum mechanical cross sections for the title reaction have been computed on the analytical potential energy surface of Pendergast, Heck, Hayes and Jaquet. The close-coupling hyperspherical method of Launay and LeDourneuf has been used for the calculations. Results explicitly shown here correspond to reaction probabilities as a function of total energy and J, integral cross sections and product rotational distributions, for the first three reactant vibrational levels and the ground j = 0 reactant rotational level. Integral cross sections confirm the main experimental findings: (a) vibrational excitation greatly enhances reactivity and (b) the reactivity threshold is near the opening of the upsilon = 2 reactant channel. Product rotational distributions show an unimodal shape, with its maximum lying at intermediate values of the open product rotational quantum numbers. Results have been compared with previously available centrifugal sudden (CS) and reactive infinite order sudden (R-IOS) results, as well as with quasiclassical trajectory (QCT) calculations. As a general trend, CS and R-IOS integral cross sections show the same qualitative shape as the exact ones, the CS ones being very close to exact but those of R-IOS are between four and five times lower. The QCT results are three times lower and fail to reproduce the threshold behaviour. CS rotational distributions are slightly hotter than exact ones, while QCT results are closer to the exact ones except for the fact that they populate rotational levels not allowed when considering both the zero-point energy and the total energy conservation.