COLLECTIVE DIPOLE OSCILLATIONS IN SMALL SILVER CLUSTERS EMBEDDED IN RARE-GAS MATRICES

The optical-absorption spectra of small mass-selected Ag(N) clusters (N = 2-2 1) embedded in solid argon are measured in the energy range 2.5-6.2 eV. Investigation of a continuous range of cluster sizes reveals the size development of the photoabsorption behavior. The main features of the spectra are in agreement with predictions based on the Nilsson-Clemenger shell model. The measured photoabsorption cross sections are consistent with a sum-rule calculation involving only s electrons. In addition, the medium influence on the spectra is studied by changing the matrix gas from argon to krypton and xenon for the cluster sizes N = 7, 11, 15, and 2 1.