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 [1] V.I. Goldansky, Nucl. Phys. 19 (1960) 482. [2] V.I. Goldansky, Nucl. Phys. 27 (1961) 648. [3] E. Olsen, M. Pfutzner, N. Birge, M. Brown, W. Nazarewicz, A. Perhac, Phys. Rev. Lett. 110 (2013) 222501.

[4] E. Olsen, M. Pfutzner, N. Birge, M. Brown, W. Nazarewicz, A. Perhac, Phys. Rev. Lett. 111 (2013) 139903. [5] I. Mukha, et al., Phys. Rev. Lett. 99 (2007) 182501. [6] M. Pfutzner, et al., Eur. Phys. J. A 14 (2002) 279. [7] J. Giovinazzo, et al., Phys. Rev. Lett. 89 (2002) 102501. [8] M. Pomorski, et al., Phys. Rev. C 83 (2011) 061303.

[9] B. Blank, et al., Phys. Rev. Lett. 94 (2005) 232501. [10] T. Goigoux, et al., Phys. Rev. Lett. 117 (2016) 162501. [11] M. Wang, G. Audi, A.H. Wapstra, F.G. Kondev, M. MacCormick, X. Xu, B. Pfeiffer, Chin. Phys. C 36 (2012) 1603.