ELECTRONIC-STRUCTURE OF SELENIUM-CLUSTERS AND TELLURIUM-CLUSTERS

The vacuum-UV-photoelectron spectra (hv = 10.0 eV or 8.3 eV) of selenium- and tellurium-clusters of different sizes (up to Se25 and Te8) were measured in a molecular beam by a photoion-photoelectron-coincidence experiment. Especially, the photoelectron spectra (4p-pi-electrons) of the selenium-clusters converge with growing cluster size to the well known spectra of amorphous solid selenium by taking into account the dielectric constant of the bulk material. The experimental results indicate the first evidence that larger selenium aggregates are van der Waals clusters of the molecules Se5, Se6, Se7 and Se8 which are contained in the equilibrium vapour.