Ab initio potential energy surface and rotationally inelastic collisions of hydroxide of lithium (LiH) with argon (Ar): State-to-state inelastic rotational cross section

Abstract

In this work, the inelastic collision of hydroxide of lithium with argon is studied for a fixed experimental value of the LiH bond length 3.0139bohr using an ab initio energy surface. The potential energy surface (PES) for the LiH(X1Σ+)–Ar(1S) Van der Waals system is calculated accurately at the ab initio coupled-cluster [CCSD(T)] with an aug-cc-pVQZ Gaussian basis set for the H and Ar atoms and cc-pVQZ Gaussian basis set for the Li atom. In this calculation, the basis set superposition error (BSSE) was corrected at all geometries with the counterpoise procedure of Boys and Bernadi. The interaction potential has a global minimum at θ=180° and at an equilibrium distance R=5.30bohr with a well depth of 525.13cm−1. This potential already fitted analytically and expanded in terms of Legendre polynomials is employed to evaluate the state-to-state rotational cross sections over a range of energies up to 6452.584cm−1. The calculations of cross sections are done in the close coupling (CC) approach. The features present on low collision energy some resonances and are related to the anisotropic interaction potential. We have compared the cross sections in LiH–Ar at 6452.584cm−1 with the available experiment one of Wilcomb and Dagdigian and the earlier calculations of Bhattacharyya et al. However, we have found that the results show a good agreement especially for j=1→0 transition.