Two long-standing puzzles in the decay of Bi185, the heaviest known proton-emitting nucleus are revisited. These are the nonobservation of the 9/2- state, which is the ground state of all heavier odd-A Bi isotopes, and the hindered nature of proton and α decays of its presumed 60-μs 1/2+ ground state. The Bi185 nucleus has now been studied with the Mo95(Nb93,3n) reaction in complementary experiments using the Fragment Mass Analyzer and Argonne Gas-Filled Analyzer at Argonne National Laboratory's ATLAS facility. The experiments have established the existence of two states in Bi185; the short-lived T1/2=2.8-1.0+2.3 μs, proton- and α-decaying ground state, and a 58(2)-μs γ-decaying isomer, the half-life of which was previously attributed to the ground state. The reassignment of the ground-state lifetime results in a proton-decay spectroscopic factor close to unity and represents the only known example of a ground-state proton decay to a daughter nucleus (Pb184) with a major shell closure. The data also demonstrate that the ordering of low- and high-spin states in Bi185 is reversed relative to the heavier odd-A Bi isotopes, with the intruder-based 1/2+ configuration becoming the ground, similar to the lightest At nuclides.

Solving the Puzzles of the Decay of the Heaviest Known Proton-Emitting Nucleus Bi 185 / D.T. Doherty, A.N. Andreyev, D. Seweryniak, P.J. Woods, M.P. Carpenter, K. Auranen, A.D. Ayangeakaa, B.B. Back, S. Bottoni, L. Canete, J.G. Cubiss, J. Harker, T. Haylett, T. Huang, R.V.F. Janssens, D.G. Jenkins, F.G. Kondev, T. Lauritsen, C. Lederer-Woods, J. Li, C. Muller-Gatermann, D. Potterveld, W. Reviol, G. Savard, S. Stolze, S. Zhu. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 127:20(2021), pp. 202501.1-202501.6. [10.1103/PhysRevLett.127.202501]

Solving the Puzzles of the Decay of the Heaviest Known Proton-Emitting Nucleus Bi 185

S. Bottoni;
2021

Abstract

Two long-standing puzzles in the decay of Bi185, the heaviest known proton-emitting nucleus are revisited. These are the nonobservation of the 9/2- state, which is the ground state of all heavier odd-A Bi isotopes, and the hindered nature of proton and α decays of its presumed 60-μs 1/2+ ground state. The Bi185 nucleus has now been studied with the Mo95(Nb93,3n) reaction in complementary experiments using the Fragment Mass Analyzer and Argonne Gas-Filled Analyzer at Argonne National Laboratory's ATLAS facility. The experiments have established the existence of two states in Bi185; the short-lived T1/2=2.8-1.0+2.3 μs, proton- and α-decaying ground state, and a 58(2)-μs γ-decaying isomer, the half-life of which was previously attributed to the ground state. The reassignment of the ground-state lifetime results in a proton-decay spectroscopic factor close to unity and represents the only known example of a ground-state proton decay to a daughter nucleus (Pb184) with a major shell closure. The data also demonstrate that the ordering of low- and high-spin states in Bi185 is reversed relative to the heavier odd-A Bi isotopes, with the intruder-based 1/2+ configuration becoming the ground, similar to the lightest At nuclides.
Settore FIS/04 - Fisica Nucleare e Subnucleare
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/888753
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