β decay of proton-rich nucleus 23Al and astrophysical consequences

We present the first study of the β decay of 23Al undertaken with pure samples. The study was motivated by nuclear astrophysics questions. Pure samples of 23Al were obtained from the momentum achromat recoil separator (MARS) of Texas A and M University, collected on a fast tape-transport system, and moved to a shielded location where β and β-γ coincidence measurements were made. We deduced β branching ratios and log ft values for transitions to states in 23Mg, and from them determined unambiguously the spin and parity of the 23Al ground state to be Jπ=5/2+. We discuss how this excludes the large increases in the radiative proton capture cross section for the reaction 22Mg(p,γ)23Al at astrophysical energies, which were implied by claims that the spin and parity is Jπ=1/2+. The log ft for the Fermi transition to its isobaric analog state (IAS) in 23Mg is also determined for the first time. This IAS and a state 16 keV below it are observed, well separated in the same experiment for the first time. We can now solve a number of inconsistencies in the literature, exclude strong isospin mixing claimed before, and obtain a new determination of the resonance strength. Both states are resonances in the 22Na(p,γ)23Mg reaction at energies important in novae. The reactions 22Mg(p,γ)23Al and 22Na(p,γ)23Mg have both been suggested as possible candidates for diverting some of the flux in oxygen-neon novae explosions from the A=22 into the A=23 mass chain