Beta decay of neutron-rich 33Mg

Zidar, Tammy
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University of Guelph

The beta-decay and beta-delayed neutron decay of a radioactive 33Mg beam provided by TRIUMF are presented in this thesis. Interest in the beta-decay daughter, 33Al comes from the fact that it lies between 32Mg, a deformed nucleus, and 34Si, outside the "island of inversion" along the N = 20 shell closure. The island of inversion around N = 20 refers to a region of the chart of the nuclides where the ground states are dominated by deformed intruder states from the fp shell, instead of the spherical sd shell states naively expected from the shell model. While originally thought to be outside the island of inversion, some 33Al studies suggest up to a 50% intruder configuration. Previously published decay schemes for 33Al, however, differ significantly. The improved efficiency of the new high purity germanium gamma-ray spectrometer, GRIFFIN, was used to perform detailed spectroscopy of 33Al following 33Mg beta-decay. Half-lives of the parent (33Mg), daughters (33Al and 32Al) and granddaughter (33Si) were determined using gamma-gated data for prominent peaks of each species present in the decay with values of 91.7(15) ms, 41.8(42) ms, 32.3(59) ms and 5.90(14) s determined, respectively. Detailed level schemes for both 33Al and 32Al were also constructed and resolve discrepancies between the previous works.

beta decay, nuclear structure