Studies of N~Z~28 nuclei with stable and radioactive heavy ion beams

• Main Author: Mohammadi, Saeed
• Published: University of Surrey 1997
• Subjects: 539.7; Nuclear physics & particle accelerators
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336807

This thesis details the study of N~Z~28 nuclei obtained using the fusion evaporation reactions 19Ne +40Ca at a beam energy of 70 MeV and 24Mg-40Ca at a beam energy of 65 MeV. The 19Ne data constitute the first tests of a neutron-deficient Radioactive Ion Beam (RIB) for high-spin nuclear spectroscopy. The radioactive Ne beam was supplied by the coupled cyclotrons at the Louvain-la-Neuve facility, Belgium. Emitted gamma-rays were detected by an array of 7 TESSA-style Ge-detectors in the backward hemisphere in two rings. A degree of channel selection was also allowed by identifying evaporated charged particles with an array of 128 silicon-strip detectors (LEDA array). Background subtraction of radiation from the decay of the beam was achieved using the timing properties of the pulsed beam and through particle detection using the LEDA charged particle array Information on the relative evaporation residue cross-sections was obtained and the problems associated with performing such experiments in a high radioactive background environment are addressed. New information on the high spin states of 58Ni was obtained using the reaction 40Ca (24Mg, alpha2p), performed at the ATLAS facility at Argonne National Laboratory. Emitted 7-rays were detected by high efficiency AYEBALL array which consisted of 18 EUROGAM and TESSA-style Compton suppressed Ge-detectors in four annular rings. Channel selection is demonstrated by use of (a) mass selection using the Argonne Fragment Mass Analyser (FMA), (b) a split anode ionization chamber at the back of the FMA, and (c) an array of 11 neutron detectors in a ring at forward angles. The effectiveness of using recoil-gated gamma coincidence data for the study of nuclear structure in neutron-deficient nuclei close to the proton drip-line is shown. The excited states of 58Ni are compared with OXBASH shell model calculations and the problems associated with forming high angular momentum states in the limited valence space are addressed.