NH(X3Σ)+H/D(2S)→H(2S) plus NH/ND(X3Σ) exchange reactions: State-to-state quantum scattering and applicability of statistical model

Quantum state-to-state dynamics for the NH+H/D -> H+NH/ND exchange reaction is reported on an accurate ab initio potential energy surface. The differential cross section is dominated by scattering into both the forward and backward directions, while the product shows strong rotational excitation. The calculated rate constant for the NH+D reaction is in excellent agreement with experiment. The applicability of a quantum statistical model is tested against exact state-to-state quantum results. Due to strong nonreactive scattering, the statistical model significantly overestimates the integral cross section. However, it is shown that the product state distribution and differential cross sections are reasonably well reproduced by the statistical model because the reactive scattering is dominated by a complex-forming mechanism. (C) 2009 American Institute of Physics. [doi:10.1063/1.3241134]