Laser spectroscopy of neutron-rich aluminium: Investigating a possible transition into the N = 20 island of inversion
Aug 1, 2025200 pages
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Thesis: PhD - ,
- Manchester U.
- Published: Aug 1, 2025
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Abstract: (U. Manchester (main))
The neutron-rich region centred around Z = 12, N = 20 marks a crucial milestone in nu- clear structure and experimental nuclear physics. While 11Be was the first isotope to exhibit deviations from conventional shell model ordering, the discovery of the N = 20 island of inversion initiated extensive studies of neutron-rich isotopes. Since Thibault et al.'s initial mass measurements of 31Na, the isotopic chains of neon, sodium, and magnesium have been well studied, revealing a region of deformation driven by n-particle-n-hole excitations across the N = 20 shell closure. Multiple nuclear observables, including electromagnetic moments, charge radii, mass measurements, and B(E2) values, have characterized this region. However, the transition from conventional shell closures in silicon (Z = 14) to strong intruder-state- driven deformation in magnesium (Z = 12) remains of interest. Positioned between these elements, aluminium (Z = 13) provides an ideal test case to probe this transition. Measurements of neutron-rich aluminium isotopes have yielded conflicting conclusions. While electromagnetic moments suggest intruder-state mixing in 33,34Al, mass measurements place them outside the island of inversion. Charge radii measurements have thus far been limited to N = 19, leaving the behaviour beyond this point unresolved. This work extends charge radii measurements beyond N = 19 and across the N = 20 shell closure to clarify the placement of 33,34Al. Neutron-rich 26-34Al isotopes were studied using Collinear Resonance Ionization Spectroscopy (CRIS) at ISOLDE, CERN. By laser scanning the 2P1/2 - 2S1/2 transition, hyperfine structures were obtained, yielding magnetic dipole moments and isotope shifts. Newly determined isotope shifts for 33,34Al provide the first charge radii measurements crossing N = 20 in this region. Comparisons with literature data reveal an increasing charge radii trend beyond N = 19, aligning with magnesium and sodium, characteristic of the island of inversion. These results suggest 33,34Al exhibit intruder-state mixing and may belong to the island, though further theoretical calculations are required for confirmation.Date of Award1 Aug 2025Original languageEnglishAwarding InstitutionThe University of ManchesterSupervisorKieran Flanagan (Supervisor) & Giles Edwards (Supervisor)- Ions
- Collinear
- Aluminium
- Isotope Shift
- Nuclear Physics
- Laser Spectroscopy
- Charge radii
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