Reactive scattering with exact propagators

Michael J. D’Mello

Walter Greiner, J. Reinhardt

Xu‐Guang Hu, Qian-Shu Li, Au‐Chin Tang

We have formulated the quantum rearrangement scattering of atom-diatomic molecules in phase space from the viewpoint of the density operators within the framework of Torres-Vega's and Frederick's phase-space representation of quantum mechanics [J. Chem. Phys. 98, 3103 (1993); 93, 8862 (1990)]. This formalism has a remarkable feature in that it naturally includes the on-the-energy-shell coherences of the initial system that are important for depicting actual scattering experiments. We have found that the full density operator describing the rearrangement scattering is closely related not only to the usual reactive transition operator T${\mathrm{^}}_{\mathrm{\ensuremath{\beta}}\mathrm{\ensuremath{\alpha}}}$, but also to the function F defined in the paper which is nonlocal in position vector and could reflect some fine structures of the reactive scattering in strong interaction region. The time-dependent reactive scattering in the quantum phase-space representation is also discussed.

Frank Großmann

We systematically extend semiclassical real-time propagation methods based on Gaussian wave packets by using the composition property of the time-dependent quantum-mechanical Green function. For the first time, in an application to the problem of barrier tunneling, a semiclassical time-domain calculation of the transmission probability exhibits good agreement with exact quantum mechanical values at energies below the barrier top. Only two insertions of unity are needed for these results in a benchmark model of reactive scattering.

Ting Xie, Lihang Li, Zhigang Sun

Abstract The log-derivative (LOGD) and renormalized Numerov (RN) methods are popularly used in inelastic and reactive scattering calculations. The computational precision of two methods and their improved versions are compared in two-body diatomic and bimolecular collisions at low temperatures. In diatomic 40K-133Cs collision example the single-channel calculations show the solution-improved RN method has the advantage over others when large fixed propagating interval used. The relative error of local scattering length in different propagating sectors are explored. In multi-channel 40K-133Cs collisions the predicted positions of Feshbach resonances by using mapping grid points indicate strong potential-following character in LOGD methods, which is consistent with the analysis on local scattering length in single-channel calculations. In multiple open-channel calculations the elastic and inelastic scatterings and their dependence on collision energy are compared as well. In bimolecular 23Na87Rb-23Na87Rb long-range reactive scattering example the elastic and reactive rate coefficients are investigated. The original LOGD method displays surprisingly relatively high accuracy with less mapping grid points and a wide range of mapping parameters. By increasing the number of mapping grid points the improved LOGD exhibits definitely superiority on precision with proper mapping parameters. We demonstrate our consequent is applicable in other colliding systems.