Rotational excitation of AlH by Helium and Neon at low temperature: State-to-state inelastic cross section

In this work, inelastic rotational collisions of AlH with He and Ne were studied. The CCSD (T) method was used for the computation of accurate two dimensional potential energy surfaces (2-D-PESs). In the calculation of the 2-D-PESs, AlH was frozen at the experimental value of 3.1149 a₀. The recently published basis sets m-aug-cc-pV (Q+d) Z of Papajak and Truhlar, completed with bond functions placed at mid-distance between the center of mass of AlH and He/Ne atom for a better description of van der Waals interaction energy, was used throughout the computational process. The PESs of AlH-He and AlH-Ne were found to have global minima at (R = 6.9 a₀, θ = 68°) and (R = 6.9 a₀, θ = 69°) respectively, with corrresponding depths of 26.32 cm^-1 and 48.70 cm^-1. These potentials were fitted analytically and expanded in terms of Legendre polynomials, then used for the evaluation of the integral cross sections of state-to-state rotational transitions in AlH induced by the collisions with He or Ne within the close coupling approach. The rate coefficients are computed for low kinetic temperatures ranging from 3 K to 300 K.