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Title: Decays of new nuclides 169Au, 170Hg, 165Pt and the ground state of 165Ir discovered using MARA
Author: Hilton, J. B.
ISNI:       0000 0004 8501 6748
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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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 WentzelKramersBrillouin (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%. Comparison of the reduced α-decay widths with systematics indicates that both α decays are unhindered. Although combining the measured α-decay Q values with extrapolated masses suggests that both new nuclides are unbound to 2-proton emission by more than 1 MeV, their α-decay halflives are too short for this decay mode to compete. Improved data were also 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.
Supervisor: Page, Robert ; Uusitalo, Juha ; Joss, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral