Absorption spectroscopy of size-selected trimers and pentamers transition metal clusters isolated in rare gas solids: Preliminary steps

Size-selected positive ionic silver trimers and pentamers and nickel trimers have been co-deposited, at low kinetic energy, with rare gas (Kr) onto a cold transparent surface. They have been neutralized onto the surface by electrons of few eV, with an efficiency of 80±20%. The optical absorption spectra of the resulting matrix-isolated neutral species have been recorded, with good sensitivity, in the UV-visible range. The evaporation of clusters, detected on the atom signal after deposition of Ni trimers of 20 eV, neutralized by electrons of 5 eV, is shown to be roughly 20%. This indicates that Ni3 clusters are present in the matrix but their number is actually too low to be optically detected. (orig.)