Theoretical studies of the (X)over-tilde (2)Pi and (A)over-tilde (2)Sigma(+) states of He center dot SH and Ne center dot SH complexes

The two-dimensional potential energy surfaces for the (X) over tilde (2)Pi and (A) over tilde (2)Sigma (+) states of the He . SH and Ne . SH complexes have been calculated using the restricted open-shell coupled cluster theor y [RCCSD(T)] and the triple-zeta augmented correlation consistent polarized basis sets with an additional (3s3p2d2f1g) set of bond functions. In the c ase of the (A) over tilde (2)Sigma (+) state of Ne . SH the entire surface has also been developed using the quadruple-zeta basis set with bond functi ons as exploratory calculations demonstrated significant differences betwee n the RCCSD(T) results obtained with the triple- and quadruple-zeta basis s ets. These potentials are somewhat shallower and less anisotropic in compar ison to the surfaces for the related He . OH and Ne . OH complexes. in cont rast to He . OH and Ne . OH, we find that the linear Rg-SH (Rg=He,Ne) confi gurations are in all but one case lower in energy than the Rg-HS geometries Variational calculations of the bound rotation-vibration states have been performed using Hamiltonians that included the RCCSD(T) potentials. The cal culated ground-vibrational-state dissociation energy, D-0, the frequency of the intermolecular stretching vibration, and the rotational constant are i n very good agreement with the available experimental results for the (X) o ver tilde (2)Pi state of both Ne . SH and Ne . SD. The energies of rotation -vibration levels for the Ne . SH and Ne . SD complexes in the (A) over til de (2)Sigma (+) state calculated using the triple- or quadruple-zeta potent ials differ significantly, but agreement with the experimental rovibrationa l transition frequencies and rotational constants is very good regardless o f which potential is used. (C) 2000 American Institute of Physics. [S0021 - 9606(00)30145-3].