Investigation of the Delta Δn=0 selection rule in Gamow-Teller transitions: The β-decay of Hg-207

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Gamow-Teller beta decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Delta n = 0 requirement plays a major role in the beta decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z = 50 (for N > 82) and Z = 82 (for N > 126). The level of forbiddenness of the Delta n = 1 nu 1g(9/2) -> pi 0g(7/2) transition has been investigated from the beta(-) decay of the ground state of Hg-207 into the single-proton-hole nucleus Tl-207 in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible gamma-ray transitions depopulating the pi 0g(7/2)(-1) state in Tl-207, an<bold> </bold>upper limit of 3.9 x 10(-3)% was obtained for the probability of this decay, corresponding to log ft > 8.8 within within a 95% confidence limit. This is the most stringent test of the Delta n = 0 selection rule to date. (C) 2019 The Authors. Published by Elsevier B.V.
© 2019 The Authors. Published by Elsevier B.V. Artículo firmado por 62 autores. Support from the European Union seventh framework through ENSAR contract no. 262010, the Science and Technology Facilities Council through grants ST/P005314/1, ST/L005743/1 and ST/J000051/1 (UK), the MINECO projects FPA2015-64969-P, FPA2015-65035-P and FPA2017-87568-P (Spain), FWO-Vlaanderen (Belgium), GOA/2015/010 (BOF KU Leuven), the Excellence of Science programme (EOS-FWO), and the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12) is acknowledged. ZsP acknowledges support by the ExtreMe Matter Institute EMMI at the GSI Helmholtzzentrum fur Schwerionenforschung, Darmstadt, Germany. PHR and SMJ acknowledge support from the UK Department for Business, Energy and Industrial Strategy via the National Measurement Office.
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