Decay studies of proton-rich nuclei in the mass 70 region and investigating their effects on the astrophysical rp-process

Proton-rich A~70 nuclei have been subject to many experimental investigations due to their accessibility since the advent of radioactive ion beams and improved experimental developments in sensitive tagging techniques. Nuclear structure data in this region are also of astrophysical significance since the (rapid proton capture) rp-process, which is believed to take place in X-ray bursts, occurs in the vicinity of the N=Z line, with rapid proton-capture chains and subsequent beta-decays allowing for the seeding of heavy elements in the A~100 region. Therefore the structure and decay properties of N~Z nuclei can have an impact on rp-process reaction rate calculations. The nuclide 72Kr, with a beta-decay half-life of 17.1(2) s, is a potential waiting point of the rp-process. However, its lifetime in a stellar environment is reduced by the two-proton capture reaction 72Kr(p,g)73Rb(p,g)74Sr. One of the main goals of the experiment was to measure the proton-separation energy, Sp, of 73Rb, by extracting the beta-delayed spectrum following the decay of 73Sr. To gain a complete picture of the two-proton capture branch for the 72Kr waiting point in the rp-process the half-life of 74Sr needs to be measured. An experiment was carried out at the Radioactive Isotope Beam Factory, RIKEN. The nuclei of interest were produced by the fragmentation of a 345 MeV/nucleon 124Xe beam on a 555 mg/cm^2 9Be target. The effects of the half-lives and proton-separation energy measured, in this work, on the effective lifetime of 72Kr have been explored using one-zone, one-dimensional reaction network calculations for the astrophysical rp-process. At the proton drip-line, a search for new isotopes and the nature of the decay of 76Y was conducted. The location of the drip line is of important interest for the rp-process. An estimate of the half-life and an upper limit of the half-life for 72Rb and 73Rb have been determined, respectively. Following these measurements, proton emission calculations have been performed by L.S. Ferreria and E. Maglione and the results are discussed in this work