Testing a Potential Averaging for Quantum Inelastic Dynamics

Abstract

To obtain the inelastic cross sections for rotation state-changing processes, two crucial ingredients are required: the intermolecular forces from ab initio quantum chemical methods and the full coupled channels (CC) treatment of the quantum scattering. The present work supports earlier work that there is a possible path which reduces the computational demands by simplifying the multidimensional potential energy surface while using the exact CC quantum dynamics to extract scattering attributes. This is applied successfully to the case of ¹¹BN^–(X²Σ⁺, j₁) in collision with H₂(X¹Σ⁺_g, j₂ = 0), the former being an anion of interest in laser cooling at cryogenic temperatures. The exact CC calculations of the quantum dynamics, using either the full four-dimensional (4D) potential energy surface (PES) or its two-dimensional (2D) averaging (discussed in the main text), show that quantum attributes from the two procedures turn out to be essentially the same. These findings indicate that the computational savings attained by reducing the dimensions of the PES while keeping the quantum dynamics exact are a realistic option for the case of the hydrogen molecule in its rovibrational ground state as a partner in low-temperature collision processes with molecular ionic species.