Structure of 24Al for the stellar reaction rate of 23Mg(p,γ)24Al

The nuclear levels of 24 Al were studied by the 24 Mg( 3 He,t) 24 Al reaction at 60 MeV. Several new states were identified including a level at 2.787 MeV just above the proton threshold in 24 Al, and considerable level shifts were observed for most levels around the threshold. The spin-parity assignments were also made for many states including the threshold states by the angular distribution measurement. This clarifies the spin-parity and the excitation energy of the critical levels assumed before for the stellar reaction rate calculation of 23 Mg(p,γ) 24 Al. A large increase of the reaction rate is predicted, based on the present experimental result, at the temperature region of T 9 = 0.2–0.8 which would be crucial for the break-out process of the NeNa cycle to the MgAl cycle. This result suggests that the onset temperature of 23 Mg(p,γ) 24 Al should be lowered roughly by 10%. Application of the ( 3 He,t) reaction at 60 MeV for spin assignment is also discussed.