Rotational cross sections and rate coefficients of aluminium monoxide AlO([formula omitted]) induced by its collision with He([formula omitted]) at low temperature

Abstract

We present the first potential energy surface (PES) for the AlO(X2Σ+)-He(1S) van der Waals complex. This PES has been calculated at the RCCSD(T) level of theory. The mixed Gaussian/Exponential Extrapolation Scheme of complete basis set [CBS(D,T,Q)] was employed. The PES was fitted using global analytical method. This fitted PES was used subsequently in the close-coupling approach for the computation of the state-to-state collisional excitation cross sections of the fine-structure levels of the AlO-He complex. Collision energies were taken up to 2500 cm-1 and they yield after thermal averaging, state-to-state rate coefficients up to 300 K. The propensity rules between the lowest fine-structure levels were studied. These rules show, on one hand, a strong propensity in favour of odd ΔN transitions, and on the other hand, that cross sections and collisional rate coefficients for Δj=ΔN transitions are larger than those for Δj≠ΔN transitions.