Off-Yrast low-spin structure of deformed nuclei at mass number A≈150

• Main Author: Krugmann, Andreas
• Format: Others
• Language: German; en
• Published: 2014
• Online Access: https://tuprints.ulb.tu-darmstadt.de/4289/13/diss_krugmann_ulb_03.pdf; Krugmann, Andreas <http://tuprints.ulb.tu-darmstadt.de/view/person/Krugmann=3AAndreas=3A=3A.html> (2014): Off-Yrast low-spin structure of deformed nuclei at mass number A≈150.Darmstadt, Technische Universität, [Ph.D. Thesis]

The present work consists of two independent parts. The first part deals with the investigation of the 0+1 -> 0+2 transition in 150Nd with inelastic electron scattering and in the second part a proton scattering experiment for the investigation of dipole excitations is presented. In the first part of this thesis a pioneer experiment in inelastic electron scattering is introduced. At an electron energy of 75 MeV, excitation energy spectra have been measured at the high resolution 169° spectrometer at the S-DALINAC. The aim of this investigation was the determination of the ρ²(E0;0+1 -> 0+2) transition strength in the heavy deformed nucleus 150Nd. The experimental form factor of this particular transition has been compared to a theoretical form factor that has been constructed by an effective density operator on a microscopic level with the help of the generator coordinate method. The required collective wave functions have been calculated in the Confined β-soft rotor model. In this model-dependent analysis the E0 transition strength has been determined for the first time. Furthermore the evolution of the E0 transition strength as a function of the potential stiffness has been investigated from the X(5) phase shape transitional point to the Rigid Rotor limit. It has been shown, that the E0 strength is relatively high at the shape-phase transitional point and starts to decrease with increasing stiffness and vanishes completely at the Rigid Rotor limit. Additionally the wave functions of the macroscopic collective Confined β-soft rotor model have been compared to those from a microscopic mean field Hamiltonian. Good agreement has been found. The second part of this thesis covers a polarized-proton scattering experiment on the heavy deformed nucleus 154Sm, that has been performed at the RCNP in Osaka, Japan. Utilizing the method of polarization transfer observables, a separation of spinflip and non-spinflip parts of the cross section has been done. Here, for the first time, the Pygmy Dipole Resonance (PDR) has been identified in the heavy deformed nucleus 154Sm that appears as a double-hump structure in the E1 response. A possible interpretation of this double-hump structure in terms of a deformation splitting analogously to the Giant Dipole Resonance (GDR) has been given. In case of the spinflip cross section, a broad distribution in the excitation energy range between 6 and 12 MeV has been observed. The distribution and the extracted sum strength are in good accordance with previous experiments.