Gamma-ray and Radioactive Decay Spectroscopy of Heavy Proton Unbound Nuclei

Establishing the limits of observable nuclei is a long-standing challenge in nuclear physics. For proton-rich nuclei, theoretical predictions suggest that these limits are determined by two-proton emission in even-Z nuclei up to Z=82 and by the emission of a single proton for odd-Z nuclei [1-4]. Two-proton radioactivity is a rare phenomenon and experimental discoveries from ground states has been limited to a few light nuclei [5 - 10]. However, extrapolations from the table of measured masses [11] combined with advances in nuclear density functional theory have allowed candidates where two-proton radioactivity competes with a-decay in heavy nuclei to be predicted.

In most cases, two-proton emission from the ground states of even-Z nuclei would occur much further from B-stability than the one-proton drip line for odd-Z nuclei due to the pairing interaction. The known cases of ground state two-proton emission in light nuclei occur around two neutrons lighter than the predicted two-proton drip line [3]. Two-proton emission from the ground states of heavy nuclei would only dominate in nuclides that lie ten or more neutrons beyond the two-proton drip line [3] and are inaccessible using current experimental facilities. However, there is a possibility that direct two-proton emission might proceed from excited states in nuclei closer to stability.

This project will use decay correlation and gamma-ray spectroscopy techniques to search for rare decay modes from long-lived excited states in heavy nuclei.

References
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