DIM modelings for realistic simulations of ionic rare-gas clusters, test on structures and photoabsorption spectra of Arn+ (n=3–8) Original Research Article

Four DIM modelings are used to study structural and spectral properties of small Arn+ clusters (n=3–8). The two modelings with the deeper Ar2+ potentials predict global minima corresponding to structures with a trimeric core, and for which the quadrimeric core structures lie clearly higher in energy. For the two others modelings, trimeric and quadrimeric core structures lie very close in energy; we expect them to play a role in experiments. Dimeric core structures correspond in all cases to stable structures, although the highest in energy. However, for two models, this energy difference systematically decreases as the cluster size increases. For the absorption spectra, three theoretical approaches have been used, namely canonical, microcanonical and quantum samplings, and compared to the available experimental results for Ar3+ and Ar8+. The theoretical results are consistent with all experimental spectra, validating the methods used and illustrating their robustness. This agreement grounds our approach for further simulations and calls for experimental measurements in wider ranges. In addition, a new presentation of the DIM theory for ionic rare-gas clusters is given. It provides more physical insight and allows for a justification of the usual zero-overlap assumption.