Abstract

The collection of proton decays observed via invariant-mass spectroscopy in this work have been applied to an array of topics in nuclear physics including the continuum effects on near-threshold resonances, the branching ratio for a quasi-bound system, and evidence for the evolution of shell structure. In the first experiment, the 6He(d,n)7Li* reaction was employed in an attempt to populate a resonance predicted by an ab initio calculation. No evidence of this resonance was found leading to a discussion on how the model needs to be improved in order to treat nuclear states above multiple thresholds. In a separate experiment, the p/gamma branching ratio for the first 2+ state of 36Ca was studied and measured to be Bp = 0.087(8). This branching ratio enabled the measurement of a B(E2, 0+_1 → 2+_1) strength of 36Ca [B(E2↑) = 131(20) e^2fm^4]. The B(E2) and branching-ratio values can be reproduced in the shell-model with the ZMB2 interaction, an interaction that predicts the Z=20 sd-shell closure is incomplete with large proton pf-shell occupancies in the ground state. This experiment also resulted in a set of reactions populating proton-rich nuclei including 35Ca and the first observations of 37Sc, 38Sc, and 34K. Proton decays for these nuclei were reconstructed, yielding three new ground-state masses and information on their low-lying structures. The newly-measured mass excesses are: ΔM(37Sc) = 3500(410) keV, ΔM(38Sc) = -4656(14) keV, and ΔM(34K) = -1487(17) keV. These masses enable us to look at trends in separation energies, which help elucidate how nuclear structure evolves, showing a fading of the Z=20 shell gap for N≤18 and indications of a N=16 subshell gap.

Committee Chair

Lee Sobotka

Committee Members

Robert Charity

Degree

Doctor of Philosophy (PhD)

Author's Department

Physics

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

10-17-2024

Language

English (en)

Author's ORCID

https://orcid.org/0000-0002-9429-0314

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