Measurement of the 2+→0+ Ground-State Transition in the Β Decay of F20

We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of 20F. A low-energy, mass-separated 20F+ beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plastic-scintillator detector. The β-decay branching ratio inferred from the measurement is bβ=[0.41±0.08(stat)±0.07(sys)]×10−5 corresponding to logft=10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on 20Ne is now known to within better than 25% at the relevant temperatures and densities.9 MoreReceived 15 August 2019Corrected 4 March 2020DOI:https://doi.org/10.1103/PhysRevC.100.065805©2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayElectron & muon captureLifetimes & widthsNuclear astrophysicsProperties20 ≤ A ≤ 38TechniquesNuclear structure & decaysRadiation detectorsRadioactive beamsShell modelSpectrometers & spectroscopic techniquesNuclear Physics