Quasi-Quantum and Full Quantum Treatments of Rotationally Inelastic CO(X¹Σ⁺)-He Scattering—Invited Paper for Atomic and Molecular Physics Data

Understanding energy transfer in atom-molecule interactions is essential for exploring and controlling molecular reaction dynamics. In this work, an ab initio potential energy surface for the CO(X¹Σ⁺)-He system was calculated at the coupled-cluster singles, doubles, and perturbative triples level, CCSD(T), using the correlation-consistent aug-cc-pVQZ basis set, and was subsequently represented by an analytical fitting function. Based on this potential energy surface, the Quasi-Quantum Treatment (QQT) and the full quantum-mechanical coupled-channel method were employed to calculate state-to-state differential and integral cross sections for rotational excitation in CO-He collisions at collision energies of 513 and 840 cm^-1. The DCS and ICS comparisons at 513 and 840 cm−1 demonstrate that the QQT-QM agreement is strongly channel dependent and does not improve uniformly across all rotational transitions at the higher collision energy. This study not only provides insight into the microscopic mechanism of collision-induced energy transfer in the CO-He system, but also offers important dynamical information for the theoretical modeling and experimental interpretation of related atom-molecule collision systems.