Coupled cluster ab initio potential energy surfaces for CO...He and CO...H2

Ab initio potential energy surfaces including the vibrational coordinate dependence are presented for CO . . . He and CO . . .H-2 using the coupled cluster method with Brueckner orbitals. The interaction energy is calculated using the supermolecule approach. The calculation of rate constants for the vibrational relaxation of CO(v = 1) by He and their comparison with the experimentally measured values over the temperature range 40-300 K is used to test the accuracy of the CO . . . He surface. Comparison with results from an earlier surface calculated by symmetry adapted perturbation theory shows that the two surfaces have similar scattering characteristics and reproduce the experimental measurements to a similar level of accuracy. The potential surface for the CO . . .H-2 system is presented as raw data in anticipation of future calculations.