Dichteabhängige Untersuchung der kollektiven Anregungen in expandiertem fluiden Rubidium

The current thesis describes the density-dependent studies of the dynamic scattering law of Rubidium in the density range from 1,48 to 0,83 gcm−3. Specific focus was given to characteristic changes of collective excitations, which indicates for a theoretically predicted instability of the electron gas, which could not be clearly proven experimentally, yet. The experimental data were obtained using the inelastic neutron scattering technique. Therefore different experiments have been performed at different neutron time-of-flight spectrometer to measure the partial differential cross section for momentum transfer of 0,3 A−1 to 2,5 A−1 as well as energy transfers of ±20 meV. Thus, the covered kinematic range includes the interesting first Brillouin zone which due to technical reasons was inacccessible until now. The static structure factors obtained by integration of the dynamic structure factors show an excellent agreement with literature and are thus an evidence of the very good quality of experimental data and their treatment. The density dependent analysis of the dynamic structure factor at the first structure factor maximum as well as in the first Brillouin zone show tremendous changes for all analyzed parameters at densities from 1,2 gcm−3 to 0,9 gcm−3. This range matches exactly the one where the instability was predicted. Moreover, parameters examined show evidence on a process of metal-nonmetal transition which significantly differs from the previous concept. It seems likely that the metallic liquid transfers into a nano-emulsion of metallic and non-metallic domains starting at densities of about 1.2 gcm−3. With further expansion the metallic domain disappears completely. This complies with a recent proposal of Hensel and Ruland regarding the density-induced metal-nonmetal transition of expanded liquid Mercury. Additionally, comparison of experimental data with literature on static structure factor show evidence that the transformation into the nano-emulsion needs an equilibration time of several hours after thermodynamic conditions are reached.