Rate coefficients of the aluminium monoxide formation by radiative association

Abstract

ABSTRACT Radiative association may be a key pathway for the formation of aluminium monoxide (AlO) in diffuse interstellar clouds, especially for the oxygen-rich asymptotic giant branch (AGB) stars. In this work, we investigated the radiative association of AlO by the collision of the aluminium and oxygen atoms in their electronic ground states, which is thought to be the most probable radiative association process. First, the potential energy curves for 12 electronic states and the dipole moments between these states were calculated by the state-of-the-art ab initio methodology. Then, the cross-sections and rate coefficients for the radiative association of AlO were computed for the temperatures in the range of 10–10 000 K. The total rate coefficients are of the order of 2.73 × 10−19–1.14 × 10−16 cm3 s−1, and the A2Π → X2Σ+, 12Δ → A2Π, 12Π → X2Σ+, and 22Σ− → A2Π transitions play a key role. The calculated results can be used to investigate the chemical evolution of dust formation in the photospheres of the oxygen-rich AGB stars.