2018ApJ...863..139T

Very recently, the optical bands of the ²Σ⁺ - X²Σ⁺system of AlO have been identified in the red supergiant star VYCMa. In an effort to explain the origin of this transition, we used state-of-the-art quantum chemical calculations with proven high accuracy to compute the lowest singlet and triplet electronic states of the AlOH and HAlO isomers as well as their equilibrium geometry and electronic properties. Our calculated potential energy surfaces implicate the three singlet electronic states 2¹A', 3¹A', and 1¹A'' in the photodissociation of the [Al,O,H] system. Only AlO, H, Al, and OH products can occur through the photodissociation of [Al,O,H]; AlH and O are not allowed. For the photodissociation of AlOH, the AlO product can occur only in its excited states AlO(²Π) and AlO(²Σ⁺).