Electronic properties of mixed barium–oxygen clusters

Abstract

Ionization potentials of BanOm clusters (2⩽n⩽13,m⩽n) have been measured by one photon ionization. These measurements, combined with relative abundances observed in mass spectra recorded under low (direct ionization) and high (dissociative ionization) laser intensity, allow to derive general trends in the evolution of the structure and stability of barium–oxide clusters. Stoichiometric clusters (BaO)n exhibit a very fast transition toward the ionic bulk barium–oxide structure while suboxides BanOn−1 exhibit a completely different behavior. In the small size range (n<9,m<5), the evolution of the electronic properties does not show any regular behavior. In particular, BanO3 present very low ionization potentials while, on the opposite, the ionization potentials of BanO4 clusters are relatively high. On the other hand, beyond n⩾9, the evolution of the electronic properties is rather smooth and a specific structural transition is observed when the oxygen/barium ratio increases.