Measurements of the radiative widths of the first T = 1, 2 + state of 20Ne and their relationship to analog β-decays

Abstract

The radiative widths for decays of the 20Ne T = 1, 2 + (10.27 MeV) state were measured by resonance α-capture in the reaction 16O(α, γ) 20Ne. A special windowless gas-cell target yielded a low-background spectrum enabling six γ-branches to be observed with a Ge(Li) detector. The six branches correspond to decays from the 10.27 MeV level to the following levels: 2 +(7.83 MeV), 2 +(7.42 MeV), 3 −(5.62 MeV), 2 −(4.97 MeV), 2 +(1.63 MeV) and 0 +(g.s.). The branching ratios and radiative widths Γ γ to these levels are: 7.83 MeV [(0.22 ± 0.06)%, 0.008 ± 0.002 eV], 7.42 MeV [(6.9 ± 0.4)%, 0.31 ± 0.04 eV], 5.62 MeV [(2.1 ± 0.2)%, 0.097 ± 0.014 eV], 4.97 MeV [(1.3 ± 0.1)%, 0.060 ± 0.008 eV], 1.63 MeV [(88.9 ± 0.5)%, 4.08 ± 0.43 eV] and 0.0 MeV [(0.64 ± 0.14)%, 0.029 ± 0.008 eV]. The radiative widths to the 1.63 MeV and 7.42 MeV levels are used to determine the CVC predictions of the weak magnetism form factors and their effects on certain β-decay observables are evaluated.