Development of novel particle spectroscopy and investigation of clustering in light neutron-rich nuclei

Pirrie, Stuart Hamilton ORCID: 0000-0001-7980-3591 (2022). Development of novel particle spectroscopy and investigation of clustering in light neutron-rich nuclei. University of Birmingham. Ph.D.

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Abstract

Nuclear cluster structures are of great interest to the nuclear physics community, providing good tests of theoretical models and exciting physics beyond the highly-successful shell model. Experiments have been performed in order to attempt to identify cluster structures in 18O, 14C and 16C. The first experiment involved precision measurements of branching ratios for high-energy states in 18O, ranging from 7 → 16 MeV. Over 50 states were investigated, with a mixture of previously measured and unmeasured branching ratios — in the case of previously measured branching ratios, typically a very good agreement was seen between this work and literature values. The values of Γα/Γtot, Ex and Γtot were extracted experimentally and used to calculate θ^2_α using the literature value of J^π, where available. These θ^2_α values were used to establish the tendency towards clustering for these states, with an emphasis on states that had previously been proposed to be members of rotational bands corresponding to cluster structures 14C + α and 12C + 2n + α. No evidence of consistent cluster structure across the proposed bands was observed, casting doubt on the existence of such cluster bands in 18O. However, some states with θ^2_α values consistent with cluster structure were observed. The second experiment, for which the analysis is ongoing, aimed to provide a proof-of-principle measurement of the ability to produce excitation functions for the compound nuclei 14C and 16C through the thick target inverse kinematics 4He(10Be,10Be)α and 4He(12Be,12Be)α resonant scattering reactions, with the 10Be and 12Be beams produced via fragmentation. The experiment also aimed to identify resonances corresponding to nuclear molecular Hoyle-state configurations, which have long since been theorised.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):