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Inner-shell photoionization spectra of Hg n clusters ( n ⩽8) have been obtained with a molecular beam experiment using synchrotron radiation from the VUV storage ring at Orsay. The photoionization spectra exhibit two strong autoionization resonances which are red-shifted with increasing cluster size. The present results are compared with solid-state experimental data which indicate that the clusters (⩽Hg 8 ) do not yet have metallic character.

Positively and negatively charged metal clusters ions generated by sputtering are investigated by a variety of experimental techniques. Gas-phase experiments include photofragmentation measurements, which reveal information about the ionization energies of silver and aluminum clusters, and gas-phase nickel carbonyl formation, from which the structures of nickel clusters are determined. In addition, the size dependence of the catalytic activity of deposited silver clusters in the development of photographic films are presented.

We report the first observation of the high vibronic levels of the ${\mathrm{Na}}_{3}$ ground state, performed by stimulated emission spectroscopy. The highest cross sections of the process, which uses the ${C}^{2}$E'' state as an intermediate state, are obtained for combinations of symmetric stretch and bending modes. These experimental results are of primary importance for the understanding of energy-level structures in systems exhibiting strong vibronic coupling.

One-photon ionization experiments were performed on K 2 and Na 3 in supersonic molecular beams using a frequency-doubled dye laser and a mass spectrometric detection system. Wavelength scans across the ionization potential of K 2 clearly indicate autoionizing Rydberg levels of low n -values and ungerade symmetry dominating the direct photoionization processes. The ionization of Na 3 , on the other hand, does not exhibit an expressed structure of autoionizing Rydberg states. Possible explanations are discussed.

Metal cluster ions were produced by means of sputtering, energy-filtered, and introduced into a tripel-quadrupole arrangement. The arrangement allowed us to perform well-controlled ion-molecule reactions with carbon monoxide. The amount of ligands of the observed carbonyl-reaction products correlates well with established electron counting rules. The ligands are extremely sensitive with respect to photo-desorption. The controlled deposition of silver cluster ions on photographic plates shows that extraordinary catalytic properties may be attributed to metal clusters of a specific size.

In chemistry there is a large number of interesting particles, whose existence is known from mass spectrometric detection. The properties of these particles, however, are almost completely unknown, because they are very unstable and they only occur in very low abundances in mixtures. Particles of this kind are — for example — fragment ions, van der Waals complexes and clusters.