Spectroscopic study of the radionuclide Na 21 for the astrophysical F 17 (α,p) Ne 20 reaction rate

The Mg24(p,α)Na21 reaction was measured at the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory to study the spectroscopy of the radionuclide Na21. A 31-MeV proton beam from the 25 MV tandem accelerator bombarded isotopically enriched Mg24 targets. Recoiling He4 particles were identified by an annular silicon strip detector array. Two energy levels at Ex=6.594 and 7.132 MeV were observed for the first time. By comparing the experimentally obtained angular distributions and distorted wave Born approximation calculations, the spins and parities of Na21 energy levels were constrained. The astrophysically-important F17(α,p)Ne20 reaction rate was also calculated for the first time using resonance parameters for 12 energy levels.