Beyond Born-Oppenheimer theory for ab initio constructed diabatic potential energy surfaces of singlet H3+ to study reaction dynamics using coupled 3D time-dependent wave-packet approach

Abstract

The workability of beyond Born-Oppenheimer theory to construct diabatic potential energy surfaces (PESs) of a charge transfer atom-diatom collision process has been explored by performing scattering calculations to extract accurate integral cross sections (ICSs) and rate constants for comparison with most recent experimental quantities. We calculate non-adiabatic coupling terms among the lowest three singlet states of H₃⁺system (⁠1¹A', 2¹A' and 3¹A') using MRCI level of calculation and solve the adiabatic-diabatic transformation equation to formulate the diabatic Hamiltonian matrix of the same process for the entire region of nuclear configuration space. The nonadiabatic effects in the D⁺ + H₂ reaction has been studied by implementing the coupled 3D time-dependent wave packet formalism in hyperspherical coordinates with zero and non-zero total angular momentum (J) on such newly constructed accurate (ab initio) diabatic PESs of ⁠H₃⁺. We have depicted the convergence profiles of reaction probabilities for the reactive non-charge transfer, non-reactive charge transfer, and reactive charge transfer processes for different collisional energies with respect to the helicity (K) and total angular momentum (J) quantum numbers. Finally, total and state-to-state ICSs are calculated as a function of collision energy for the initial rovibrational state (⁠ v= 0, j = 0) of the H₂ molecule, and consequently, those quantities are compared with previous theoretical and experimental results.