Anion photoelectron spectroscopy of transition metal- and lanthanide metal-silicon clusters: MSi(n) (-) (n=6-20).

The electronic properties of silicon clusters containing a transition or lanthanide metal atom from group 3, 4, or 5, MSi(n), (M=Sc, Ti, V, Y, Zr, Nb, Lu, Tb, Ho, Hf, and Ta) were investigated by anion photoelectron spectroscopy at 213 nm. In the case of the group 3 elements Sc, Y, Lu, Tb, and Ho, the threshold energy of electron detachment exhibits local maxima at n=10 and 16, while in case of the group 4 elements Ti, Zr, and Hf, the threshold energy exhibits a local minimum at n=16, associated with the presence of a small bump in the spectrum. These electronic characteristics of MSi(n) are closely related to a cooperative effect between their geometric and electronic structures, which is discussed, together with the results of experiments that probe their geometric stability via their reactivity to H(2)O adsorption, and with theoretical calculations.