Rotational excitation of 36ArH+ by He at low temperature.

In this paper, we focus on the determination of the rotational excitation rate coefficients of the first observed molecule containing noble gas ³⁶ArH⁺ isotope by He. Hence, we present the first potential energy surface (PES) of ArH⁺ --He van der Waals system. The interaction PES of the ArH⁺ (X¹ Σ⁾⁺-He(¹S) complex is calculated by the ab initio explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in connection with the augmented correlation consistent triple zeta Gaussian basis (aug-cc-pVTZ). The interaction potential presents two global minima of 708.00 and 172.98 cm^-1 below the ArH⁺ (X¹ Σ ⁺)-He(¹S) dissociation limit. Using the PES obtained, we have computed integral inelastic cross-sections in the close-coupling approach among the first 11 rotational levels of ArH⁺ for energies up to 2500 cm^-1. Downward rate coefficients were determined at low temperature (T ≤ 300 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments. [ABSTRACT FROM AUTHOR]