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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.

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.

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.

Inner-shell autoionization spectra obtained with synchrotron radiation are reported for mercury clusters ${\mathrm{Hg}}_{n}$, $n\ensuremath{\le}40$. For the small clusters $n\ensuremath{\le}12$ the spectral behavior as a function of size is interpreted in terms of an excitonic model. For larger cluster sizes a gradual deviation from van der Waals bonding is observed. The asymmetry occuring in the line profiles reflects the progressive construction of the $\mathrm{sp}$ conduction band.