Interaction-Asymptotic Region Decomposition Method for a Triatomic Reactive Scattering with Symmetry Adoption.

For solving the "coordinate problem" in a product state-resolved calculation with the quantum wave packet method, an interaction-asymptotic region decomposition (IARD) method has been proposed for a general triatomic reactive scattering process. In the IARD method, the three asymptotic regions are represented by the corresponding Jacobi coordinates, but the hyperspherical coordinate is applied for representing the interaction region. For a triatomic reaction A + B2 with symmetry, explicit inclusion of all three channels in the calculations is unnecessary. Thus, numerical methods for exploring the symmetry of the A + B2 reaction need to be developed. Due to the symmetry of reactant B2, spherical harmonics with only even or odd number are required for representing the angular degree of freedom in the reactant channel and only one product channel needs to be considered. For representing the interaction region, the symmetry in the hyperspherical coordinate could also be explored to reduce the computational effort. The advantages of the IARD method with symmetry adoption were illustrated by calculating the product state-resolved reaction probabilities of the 16O + 36O2, 18O + 32O2, F + H2, and D+ + H2 reactions in the ultracold collision region. The numerical results calculated using the famous ABC code and the reactant coordinate-based method were provided for comparison.