Solving the Puzzles of the Decay of the Heaviest Known Proton-Emitting Nucleus 185Bi
Abstract
Two long-standing puzzles in the decay of 185Bi, 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 -μ s 1 /2+ ground state. The 185Bi nucleus has now been studied with the 95Mo (93Nb, 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 185Bi; the short-lived T1 /2=2.8-1.0+2.3 μ s , proton- and α -decaying ground state, and a 58 (2 )-μ s 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 (184Pb) with a major shell closure. The data also demonstrate that the ordering of low- and high-spin states in 185Bi 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.
- Publication:
-
Physical Review Letters
- Pub Date:
- November 2021
- DOI:
- 10.1103/PhysRevLett.127.202501
- Bibcode:
- 2021PhRvL.127t2501D