Proton Threshold States in ALUMINUM-26 and Their Role in Astrophysics.

The energy levels of ('26)Al between E(,x) = 6.3 and 6.5 MeV, corresponding to proton threshold energies in the ('25)Mg+p reaction from E(,p) = 0 to 200 keV, have been investigated using the reactions ('27)Al(('3)He,(alpha))('26)Al and ('24)Mg(('3)He,p)('26)Al. Despite early work reporting a doublet at E(,x) = 6346 keV and E(,x) = 6362 keV, most subsequent work reported a single state with conflicting spin and parity assign- ments. Our work clearly establishes the presence of the doublet and resolves the conflicts. We find that there are six states in this excitation energy region, including a new state at E(,x) = 6410 (+OR-) 5 keV. The L-values leading to possible spin and parity assignments for all these states have been made using DWBA. By measuring the spectroscopic factors of these states from the ('25)Mg(('3)He,d)('26)Al reaction, resonance strengths, (omega)(gamma), of the proton threshold states in ('26)Al corresponding to the ('25)Mg(p,(gamma))('26)Al reaction have been deduced. The limits on the branching ratios from these states to the ground state of ('26)Al have been obtained by using the reaction ('27)Al(('3)He,(alpha)(gamma))('26)Al. Finally by combining the results of the above experiments, stellar reaction rates of the ('25)Mg(p,(gamma))('26)Al reaction have been calculated. Our results conclude that the production rate of ('26)Al in stellar environments from the reaction ('25)Mg(p,(gamma))('26)Al is substantially higher than what was calculated from other work.