Gamma decays of some T=0, T=1 and T=2 states above E_X=9.5 MeV in ²⁰Ne

Abstract

Coincidence studies of the ¹⁹F(³He, dγ) reaction and observation of ¹⁶O(α, γ₁) and ¹⁶O(α, α′γ_6.13) resonances have been used to investigate the properties of states in ²⁰Ne at 9.88±0.03 MeV, 10.271±0.004 MeV, 10.89±0.03 MeV, 11.59±0.03 MeV, 12.216±0.005 MeV(Γ<100 eV), 12.254±0.005 MeV (Γ≈5 keV) and 12.397±0.008 MeV (Γ≈25 keV). The observed γ-ray branching ratios support assignments of J^π=3⁺ for the levels at 9.88, 10.89 and 11.59 MeV. For the 12.216 MeV level, resonance studies require J^π=2⁺; the strongly hindered α-decay (Γ_α<1.34 eV) leads us to assign T=1. This level has Γ_γ1>0.3 eV and $\text{Γ}{}_{\mathrm{\gamma 0}}\text{Γ}{}_{\mathrm{\gamma 1}}\text{≦0.015}$. The ¹⁶O(α, γ₁) resonance strengths correspond to $\text{ωΓ}{}_{\mathrm{\alpha }}\text{Γ}{}_{\mathrm{\gamma 1}}\text{Γ}\text{=1.46±0.22}$ and 3.9±0.8 eV for the resonances at 12.216 and 12.254 MeV, respectively. The effect of these results on the previously measured radiative width of the second T=2 state in ²⁰Ne is discussed. The 12.397 MeV level has J^π=3⁻, in disagreement with a recent assignment of 1⁺.