Comparison of quantum scattering calculations for the H + H2 reaction using the LSTH and DMBE potentials

Abstract

The results of a comparison of quantum scattering calculations based on the S-matrix version of the Kohn variational principle, using the Liu–Siegbahn–Truhlar–Horowitz (LSTH) and double many-body expansion (DMBE) potential-energy surfaces for the H + H₂ reaction, are reported. We focus on the particular state-to-state cross-sections [(v= 0, j= 0)→(v′= 1, j′= 1, 3)] for which there is an unresolved discrepancy between experimental and theoretical results, in order to estimate the sensitivity of the theoretical results to the accuracy of the potential. The potentials differ most significantly in their bending dependence near the H₃ transition state. The difference between the potentials at the saddle point varies between 1 and 2% for various fixed angles. Partial cross-sections are presented for total J= 0 and 10 over a wide range of energy (0.9–1.3 eV total energy). The energy-dependent state-to-state cross-sections for the above transitions are quite insensitive to the difference between the potentials for all values of total J considered. The product state distributions for the energies at which scattering resonances have been experimentally reported are similarly insensitive to the difference in the H₃ bending potential. We conclude from this brute-force comparison that the accuracy of the quantum scattering calculations is not subject to anomalous sensitivity.