Alpha-particle decay widths of levels in 19F

Levels of 19F in the excitation region 4<Ex<11 MeV were studied with the 12C(11B, α) reaction, using a recoil-coincidence technique to measure values of Γγ/Γ. The information obtained has been combined with known values of ω γ to determine alpha-particle widths in the range ∼ 1-100 eV for various levels. The highest lying level observed to have a significant gamma-decay probability was a new level at Ex = 10.927 ± 0.008 MeV with Γγ/Γ = 0.051 ± 0.004. The 11/24-, 9.873 MeV level was observed to have a surprisingly large value for Γγ/Γ of 0.43 ± 0.04, which gives Γα = 1.4 ± 0.3 eV, Γρ = 0.10 ± 0.03 eV, and a total width Γ 2.6 ± 0.4 eV. The present measurements of Γα for the 11/21- and 11/24- levels, together with previous information for the 11/22- and 11/23- levels, provide for the first time a complete unambiguous picture of the distribution of alpha-strength among these 11/2- levels and clarify a long outstanding problem concerning the 11/2- member of the Κπ = 1/2- alpha-cluster band. We conclude that the 11/22-, 8.953 MeV level is the best candidate for this alpha-cluster state, and there is very little configuration mixing among the 11/2- levels. 2 figs., 6 tabs