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Title: Experimental measurements of break-up reactions to study alpha clustering in carbon-12 and beryllium-9
Author: Smith, Robin
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2017
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Due to the high binding energy of the α-particle, this object can preform in heavier atomic nuclei. This work explores α-clustering in ⁹Be and ¹²C by measuring their nuclear break-up. For ⁹Be, it has been proposed that the two α-particles of the unstable ⁸Be nucleus are bound together by a covalently shared neutron. This thesis reports the observation of a state in ⁹Be at 3.8 MeV through the ⁹Be(⁴He,α)ααn reaction. By comparing its reduced width with that of a potential mirror analogue in ⁹Be, its angular momentum was shown to be J < 7/2. This is consistent with a hitherto unmeasured 3/2⁺ molecular binding configuration state. The ¹²C nucleus is thought to consist of three α-clusters and its famous Hoyle state has been shown to possess an unusually large volume. Due to its low density, this state may behave like a Bose-Einstein condensate, where the fermonic structures of the constituent α-particles are no longer important. By precisely measuring the decay of the Hoyle state into three α-particles, through the ¹²C(⁴He,α)3α reaction, an upper limit for the direct 3α decay branch of 0.047% was obtained. This lies below predictions for the decay of a condensate state, casting doubt on this interpretation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics