beta decay of proton-rich nucleus Al-23 and astrophysical consequences
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
We present the first study of the decay of Al23 undertaken with pure samples. The study was motivated by nuclear astrophysics questions. Pure samples of Al23 were obtained from the momentum achromat recoil separator (MARS) of Texas A&M University, collected on a fast tape-transport system, and moved to a shielded location where and - coincidence measurements were made. We deduced branching ratios and log ft values for transitions to states in Mg23, and from them determined unambiguously the spin and parity of the Al23 ground state to be J=5/2+. We discuss how this excludes the large increases in the radiative proton capture cross section for the reaction Mg22(p,)Al23 at astrophysical energies, which were implied by claims that the spin and parity is J=1/2+. The log ft for the Fermi transition to its isobaric analog state (IAS) in Mg23 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 Na22(p,)Mg23 reaction at energies important in novae. The reactions Mg22(p,)Al23 and Na22(p,)Mg23 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. 2006 The American Physical Society.
