An ab initio study of the potential energy surface and spectrum of Ar–CO

The two-dimensional potential energy surfaces for the Ar–CO complex have been developed using single and double excitation coupled-cluster theory with noniterative treatment of triple excitations [CCSD(T)]. The most accurate results have been obtained with the augmented correlation-consistent polarized triple zeta basis set (aug-cc-pVTZ) with an additional (3s3p2d2f1g) set of bond functions. The minimum of −104.68 cm−1 has been found at (R,Θ)=(3.714 Å, 92.88°), where R and Θ denote the Jacobi coordinates with Θ=0° corresponding to the linear Ar–OC geometry and Θ=180° to the linear Ar–CO geometry. Dynamical calculations have been performed to determine the frequencies of various rotational and rovibrational transitions. The overall agreement with experiment is good. For example, the calculated frequencies of the intermolecular bending and stretching vibrations, 12.015 and 18.520 cm−1, respectively, agree very well with the experimental values (12.014 and 18.110 cm−1).