Photoelectron spectra of mass-separated Nb n Ϫ clusters reveal an even/odd alternation for nϭ6-17, indicating a closed electronic shell of the neutral even-numbered clusters. The HOMO-LUMO gap of Nb 8 , Nb 10 , and Nb 16 is found to be larger than that of the other even-numbered clusters, which correlates with the low H 2 reactivities of these species. The spectrum of Nb 15 Ϫ is different from all other clusters in this size range, which might be an indication for a geometric bcc shell closing. The influen e of the electronic structure of the clusters on the reactivity is discussed.

Photoelectron spectroscopy measurements and density functional theory calculations are combined to determine structures of Nb 2 n (n 3 8) clusters. A detailed comparison between observed and calculated electronic binding energies shows that the clusters have low-symmetry compact 3D structures and the lowest possible total spin, except for the three-and five-ato clusters which are in triplet states. We fin evidence for the coexistence of two isomers of Nb 2 8 under some experimental conditions. This approach shows great promise for structural characterization of small clusters.

Fluoroalkylsilanes (FAS) prove to be an interesting water-repellent coating for the recently discussed "superhydrophobic surfaces". The FAS investigated here form a self-assembled monolayer when brought into contact with a surface. They arrange at a high degree of orientation with their molecular axis perpendicular to the substrate surface. The film stability and the film thickness were observed using X-ray photoelectron spectroscopy. The orientation of the FAS molecules was investigated with polarizationdependent X-ray absorption near edge spectroscopy (XANES). Furthermore using density functional theory the molecular structure was calculated in order to aid in the interpretation of the polarization dependence of the XANES spectrum at F K-edge.

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