A CCSD(T) STUDY OF THE HE-CENTER-DOT-NO MOLECULAR-COMPLEX

Calculations at the CCSD(T) level of theory employing the cc-pVTZ, aug -cc-pVTZ and aug-cc-pVqZ basis sets are reported. Both the (2)A' and t he (2)A '' states are considered, as well as the two linear structures , He . NO and He . ON. The highest level of calculation, CCSD(T)/aug-c c-pVQZ//CCSD(T)/aug-cc-pVTZ, indicates that the global minimum is a sk ewed T-shaped structure, in agreement with recent CEPA calculations, b ut in disagreement with MP4 calculations, which concluded that the lin ear He . ON isomer was the lowest energy geometry. Although the highes t level of theory used here indicates that the (2)A' surface is the lo wer in energy, the ordering of the (2)A' and the (2)A '' surfaces has not yet been firmly established. The interaction energy is calculated to be similar to 27 cm(-1), and estimated as being similar to 30 cm(-1 ) at the basis set limit. (C) 1998 American Institute of Physics. [S00 21-9606(98)01525-6].