Inelastic scattering of Ni and Zn isotopes off a proton target

• Main Author: Cortes Sua, Martha Liliana
• Format: Others
• Language: en
• Published: 2016
• Online Access: https://tuprints.ulb.tu-darmstadt.de/5595/1/Cortes_PhDThesis.pdf; Cortes Sua, Martha Liliana <http://tuprints.ulb.tu-darmstadt.de/view/person/Cortes_Sua=3AMartha_Liliana=3A=3A.html> (2016): Inelastic scattering of Ni and Zn isotopes off a proton target.Darmstadt, Technische Universität Darmstadt, [Ph.D. Thesis]

Inelastic proton scattering of 70,72,74Ni and 76,78,80Zn was performed at the RIBF facility of the RIKEN Nishina Center, Japan, as part of the first SEASTAR campaign. Radioactive isotopes were produced by the in-flight fission of a beam of 238U ions incident on a 3 mm thick Beryllium target. After production, neutron-rich radioactive isotopes were selected and identified on an event-by-event basis using the BigRIPS separator. Selected isotopes of interest were focused onto the liquid hydrogen target of the MINOS device and gamma-rays from inelastic (p, p') reactions were detected with the DALI2 array, consisting of 186 NaI crystals. Outgoing beam-like particles were identified using the ZeroDegree spectrometer. Gamma-rays produced in the reaction were Doppler corrected and the first 2+ and 4+ states in all the isotopes were identified. Detailed data analysis was performed including the implementation of algorithms that discriminate events where more than one particle was present. Using detailed Geant4 simulations, exclusive cross-sections for inelastic proton scattering were obtained. Deformation lengths were deduced from the experimental cross-sections using the coupled-channel calculation code ECIS-97. The deformations lengths of 72,74Ni and 76,80Zn were found to be fairly constant at a value of 0.8(2) fm, suggesting similar vibrational amplitudes, while the isomeric presence in the secondary beams of 70Ni and 78Zn allowed only lower limits for those two isotopes. By combining the deformation lengths with the known B(E2; 0+ -> 2+) values, the neutron-to-proton matrix element ratios, Mn/Mp, were obtained. A clear indication of the closed proton shell in the 72,74Ni could be observed, as Mn/Mp > N/Z, indicating an increased contribution of the neutrons to the vibrational amplitude. For the case of 76,80Zn, Mn/Mp < N/Z, indicating an open proton shell.