Molecule-doped rare gas clusters: structure and stability of ArnNO(X2 Pi1/2, 3/2), n is less than or equal to 25, from new ab initio potential energy surfaces of ArNO

High level ab initio calculations carried out for the 2Aʹ and 2Aʹʹ states of ArNO(X2Pi) predict a crossing near the T-shape configuration, with the 2Aʹ minimum being slightly deeper. Spin-orbit coupling is included through a model treatment and results in two potential energy surfaces with similar topologies, nearly parallel to each other and close to the averaged non-relativistic surface. These results are used to construct a DIM-like model for ArnNO clusters. The lowest energy cluster structures are found to resemble those for Arn+1 with NO lying in the surface. The set of major magic numbers (structures of pronounced stability) is also the same as for the Arn+1 clusters, and is emphasized further by the detachment of NO, which requires a larger energy than for detachment of a single Ar atom. The relations of the difference between the two dissociation energies and of the ArnNO(1/2 to 3/2) excitation energy to the magic numbers are discussed.