Struktur und Energierelaxation elektronisch angeregter "3He- und "4He-Cluster

Abstract

The structure and relaxation dynamics of electronically excited "3He- and "4He clusters are investigated using time- and energy-resolved luminescence spectroscopy. He clusters are ideal model systems for studying the changes of electronically excited states between atoms and many body systems because of their relatively simple electronic structure. A remarkable feature of He clusters is the fact that the density can be varied over 4 orders of magnitude depending on the cluster size and the isotope. Moreover, He clusters are good candidates for investigating relaxation dynamics using luminescence spectroscopy, because in liquid He the coupling between the electronically excited states is weak compared to other pure systems leading to a strong emission of discrete lines in the near infrared and visible range, due to transitions between electronically excited states. The absorption bands of "3He-and "4He clusters although similar have different energies and widths. The bands can be assigned to transitions into perturbed, excited atomic states. The observed correlation of the energies and the line widths of the spectral features with the average density confirms the assignment to atomic excited states in the clusters and excludes excitons. (orig.)182 refs.Available from TIB Hannover: RR 8919(1999-028) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman