Spectroscopy and characterisation of high multipolarity transitions depopulating the metastable state in ⁵³Fe

Abstract

Spectroscopy and characterisation of high multipolarity transitions depopulating the metastable state in ⁵³Fe Abstract: This thesis reports the observation of high multipolarity transitions depopulating the T1=2 = 2.54 minute, Jπ = 19=2⁻ state in ⁵³Fe, populated via the ⁵¹V(⁶Li,4n) and ²⁴Mg(³²S,2pn) reactions at 50 and 90 MeV, respectively. Excited states were populated using beams pulsed on multi-minute timescales delivered from the ANU 14UD accelerator, with γ-ray decays collected over 20 minute cycles. A time subtraction of the latter 10 minutes of data collection from the first 10 minutes, obtained relatively clean spectra, free from background contamination. Sum-coincidence contributions to the weak E6 and M5 decay branches have been quantified using two different detector geometries, while several methods for the estimation and measurement of sum-coincidence intensity have been employed, obtaining final γ-ray branching ratios of 0.00059(7) and 0.0112(7) for the E6 andM5 transitions, respectively. A comprehensive reviewof E4,M5 and E6 transitions in atomic nuclei has been attempted and the nature of these transitions has been discussed within the shell model framework.