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

Abstract

Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both (for ) and (for ). The level of forbiddenness of the g7/2 transition has been investigated from the decay of the ground state of 207Hg into the single-proton-hole nucleus 207Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g state in 207Tl, an upper limit of % was obtained for the probability of this decay, corresponding to within a 95% confidence limit. This is the most stringent test of the selection rule to date.