Exploration of mass-selected clusters by soft x-ray synchrotron radiation is well suited to receive element specific information on clusters in contact with a support and to systematically follow the evolution of size-dependent electronic and geometrical properties from the smallest clusters toward the bulk. Here we describe an experimental setup, which combines cluster synthesis, mass selection, soft landing, ultrahigh vacuum transfer, and photoionization experiments such as x-ray photoelectron spectroscopy, x-ray absorption, and Auger electron spectroscopy. First spectroscopic results and experimental conditions are briefly discussed for Cu(19) deposited onto the natural oxide layer of a Si-wafer surface.

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Excitation-energy dependent Auger spectra of small copper clusters supported by a thin silica layer have been measured as function of cluster size. The Auger kinetic energy of the clusters clearly changes with the excess energy of the emitted photoelectron while not for the bulk. The kinetic energy shift is attributed to post-collision interaction (PCI) and exhibits a reduced metallic screening ability of small Cu-clusters. The spectroscopic data reveal an evolution from a long-range Coulomb-like interaction to a short-range "screened" electrostatic interaction within the sub-nm range. The data show that core electron spectroscopy such as PCI-Auger measurements can be used as a general tool to follow the metallic character of supported clusters.