2020

Hilton, Joshua Ben

New nuclides 169Au, 165Pt and 170Hg and new ground state 165Irg were produced using reactions of 96Ru(78Kr,XpXn) at bombarding energies of 390 MeV and 418 MeV and 92Mo(78Kr,XpYn) at a bombarding energy of 418 MeV. The MARA vacuum mode recoil mass separator was used to separate the new nuclei and implant them into a DSSD instrumented with digital readout electronics to measure their decay properties. The proton-emitting nuclei were identified using digitised preamplifier output ‘traces’, and the method used is discussed in depth. Fifteen proton-decay chains of 169Aum were measured with proton-emission energy Ep = 2182(28) keV and half-life T1/2 = 1.27+0.61 −0.57 µs. One α-decay chain of 169Aum was also identified with α-particle energy Eα = 7333(27) keV, which occurred 1.3 µs after the recoil ion was implanted. Combining the data for both decay branches yielded a half-life of 1.16+0.50 −0.47 µs and an estimated production cross section of 5 nb for this state in 169Au. Seven proton-decay chains of 165Irg were measured with proton emission energy Ep = 1454(38) keV and T1/2 = 1.20+0.82 −0.74 µs. The results are compared with Wentzel–Kramers–Brillouin (WKB) calculations.The prospects of observing proton emission from even lighter gold and iridium isotopes are discussed. Four α-decay chains of 165Pt were measured with α-particle energy Eα = 7272(14) keV and T1/2 = 0.26+0.26 −0.09 ms, with an assumed α branching ratio of ≈100%. One α-decay chain of 170Hg was measured with Eα = 7590(30) keV and T1/2 = 0.08+0.40 −0.04 ms, with an assumed α branching ratio of ≈100%. Reduced α-decay widths were compared with systematic data in the region, indicating that both α decays are unhindered. Combining the α-decay Q values measured with extrapolated masses indicates that the new nuclides are both unbound to 2-proton emission by >1 MeV. However, this decay mode does not compete as their α-decay half-lives are too short. Improved data were obtained for the α emitters 166,167Pt, produced via the 96Ru(78Kr,α4n) and 96Ru(78Kr,α3n) reactions at bombarding energies of 390 MeV and 418 MeV, respectively. The results of this thesis are presented in 2 refereed publications [1, 2].