Rotational excitation induced by collision of AlOH with helium

Abstract

The present paper deals with the calculation of rate coefficients for the 16 first rotational levels of the AlOH molecule in its ground vibrational state, induced by collision with helium. Such data are useful for studies of low-temperature interstellar environments. A new potential energy surface (PES) for the AlOH-He system, calculated at a AlO and OH r-distance frozen at their experimental equilibrium distances (r ₁[Al-O]=3.1796a ₀ and r ₂[O-H]=1.6597a ₀) was obtained by using the CCSD(T) ab initio method associated with the basis sets aVQZ, completed with bond functions placed at mid-distance between the center of mass of AlOH and its projectile. Dynamical calculations of pure rotational (de)excitation of AlOH-He were performed within the close-coupling method and the collisional cross-sections for the 16 first rotational levels of AlOH were calculated for the kinetic energies up to 1500 cm⁻¹. State-to-state rate coefficients were computed for the temperatures ranging from 3 K up to 170 K. We found that the ΔJ=1 transitions are dominant and a propensity rule that favors odd ΔJ transitions is observed.