Rydberg states of small NaArn* clusters

Abstract

The 4s and 5s Rydberg excited states of NaArn* clusters are investigated using a pseudopotential quantum-classical method. While NaArn clusters in their ground state are known to be weakly bound van der Waals complexes with Na lying at the surface of the argon cluster, isomers in 4s or 5s electronically excited states of small NaArn* clusters (n≤10) are found to be stable versus dissociation. The relationship between electronic excitation and cluster geometry is analyzed as a function of cluster size. For both 4s and 5s states, the stable exciplex isomers essentially appear as sodium-centered structures with similar topologies, converging towards those of the related NaArn+ positive ions when the excitation level is increased. This is consistent with a Rydberg-type picture for the electronically excited cluster, described by a central sodium ion solvated by an argon shell, and an outer diffuse electron orbiting around this NaArn+ cluster core. © 2006 American Institute of Physics.