Constraining 26 Al 1 p resonances using 26 Al „ 3 He , d ... 27

Interest in the origin of Al following observation of its decay radiation in the galactic plane @1–6# and its isotopic residues in meteorites @7,8# has prompted measurements of the reactions involved in its production and destruction. Prior to the present work, resonances in the Al~p ,g!Si destruction reaction as low as Ep5288 keV had been observed directly @9#. Spectroscopy of transfer reactions on stable targets by Wang et al. @10# and others @11# has revealed seven states in Si at lower energies ~Fig. 1!. Some of the proposed Al production sites involve temperatures below 10 K ~T950.1! at which one of these lower states could dominate the reaction rate. Since the J55 ground state of Al strongly favors formation of high-spin states in Si, the spins ~as well as spectroscopic strengths! of the observed states are needed. Because Wang et al. @10# could not extract this information directly from their data, they identified low-spin states in the analogous region in Al in an effort to eliminate from further consideration states in Si which could not correspond to astrophysically interesting resonances. To avoid this dependence on uncertain analog assignments, we developed a thin target of radioactive Al to ex-