Potential energy surface and rovibrational states of the ground Ar-HI complex.

A potential energy surface for the ground electronic state of the Ar-HI van der Waals complex is calculated at the coupled-cluster with single and double excitations and a noniterative perturbation treatment of triple excitations [CCSD(T)] level of theory. Calculations are performed using for the iodine atom a correlation consistent triple-zeta valence basis set in conjunction with large-core Stuttgart-Dresden-Bonn relativistic pseudopotential, whereas specific augmented correlation consistent basis sets are employed for the H and Ar atoms supplemented with an additional set of bond functions. In agreement with previous studies, the equilibrium structure is found to be linear Ar-I-H, with a well depth of 205.38 cm(-1). Another two secondary minima are also predicted at a linear and bent Ar-H-I configurations with well depths of 153.57 and 151.57 cm(-1), respectively. The parametrized CCSD(T) potential is used to calculate rovibrational bound states of Ar-HI/Ar-DI complexes, and the vibrationally averaged structures of the different isomers are determined. Spectroscopic constants are also computed from the CCSD(T) surface and their comparison with available experimental data demonstrates the quality of the present surface in the corresponding configuration regions.