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 be en 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 polari zed 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,Thet a)=(3.714 Angstrom, 92.88 degrees), where R and Theta denote the Jacobi coo rdinates with Theta = 0 degrees corresponding to the linear Ar-OC geometry and Theta = 180 degrees to the linear Ar-CO geometry. Dynamical calculation s have been performed to determine the frequencies of various rotational an d 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 w ell with the experimental values (12.014 and 18.110 cm(-1)). (C) 2000 Ameri can Institute of Physics. [S0021-9606(00)30310-5].