In-beam gamma and electron spectroscopy of 253No

Mistry, Andrew
In-beam gamma and electron spectroscopy of 253No. PhD thesis, University of Liverpool.

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The (S)ilicon (A)nd (Ge)rmanium (sage) spectrometer has been employed, together with the ritu gas-filled separator and the great focal plane spectrometer with Total Data Readout (TDR) at the University of Jyv¨askyl¨a to analyse the heavy actinide nucleus 253No (Z=102). Initially, the neutron-deficient odd-A isotope 177Au (Z=79) is studied using the recoil-decay tagging technique, enabling testing and demonstration of γ ray and conversion electron coincidence analysis techniques using sage. This has allowed for conversion coefficient measurements on a number of low-lying states. The main focus of the study is on 253No with combined in-beam γ ray and electron spectroscopy through the recoil-tagging technique. Orbitals emanating from the next shell closure above 208Pb are sensitive to measurement in the deformed heavy midshell region. Thus probing the single-particle structure of regional midshell heavy nuclei allows for exploration of the island of enhanced stability toward the next closed nucleon shells. Using 253No data from sage has enabled γ-electron coincidences to be established for level scheme construction with transition energies determined. Recoil-tagged prompt γ ray and internal conversion electron spectra are compared to Monte Carlo simulations to confirm the rotational structure nature of the bands. Internal conversion coefficient measurements establish the multipolarity of transitions within the bands. Measurement of the B(M1+E2’)/B(E2) interband-intraband ratio confirms the assignment of the bandhead configuration, with results presented strongly supporting the 9/2−[734]ν observed in previous studies. An isomeric state is measured with T1/2=28.6±2.3 µs confirmed through a decay via a 167 keV M2 transition resulting from the 5/2+[622]ν configuration. A 608±20 µs slower isomer has also been tentatively measured, potentially with decay through a non-yrast structure. Excited 249Fm states following the α-decay of 253No are also measured through the recoil-decay tagging technique.

Item Type: Thesis (PhD)
Additional Information: Date: 2014-10-15 (completed)
Depositing User: Symplectic Admin
Date Deposited: 10 Feb 2015 11:17
Last Modified: 17 Dec 2022 00:48
DOI: 10.17638/02003299