Predicting the Photoelectron Spectra of Quasi Octahedral Al6Mo- Cluster

Paulo H. Acioli, Northeastern Illinois University


We have recently developed a computational methodology to separate the effects of size, composition, symmetry and fluxionality in explaining the experimental photoelectron spectra of mixed-metal clusters. This methodology was successfully applied first in explaining the observed differences between the spectra of Al13- and Al12Ni- and more recently to explain the measured spectra of AlnMo-, n=3–5,7 clusters. The combination of our approach and new synthesis techniques can be used to prepare cluster-based materials with tunable properties. In this work we use the methodology to predict the spectrum of Al6Mo-. This system was chosen because its neutral counterpart is a perfect octahedron and it is distorted to a D3d symmetry and was not observed in the recent experiments. This high symmetry cluster bridges the less symmetric Al5Mo- and Al7Mo-structures.The measured spectra of Al5Mo- has well defined peaks, while that of Al7Mo-does not. This can be explained by the fluxionality of Al7Mo-, as at least 6 different structures lie within the range that can be reached by thermal effects. We predict that Al6Mo- has well defined peaks, but some broadening is expected as there are two low-lying isomers, one of D3d and the second of D3h symmetry that are only 0.052 eV apart.