{beta} decay of proton-rich nucleus {sup 23}Al and astrophysical consequences
- Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
We present the first study of the {beta} decay of {sup 23}Al undertaken with pure samples. The study was motivated by nuclear astrophysics questions. Pure samples of {sup 23}Al 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 {beta} and {beta}-{gamma} coincidence measurements were made. We deduced {beta} branching ratios and log ft values for transitions to states in {sup 23}Mg, and from them determined unambiguously the spin and parity of the {sup 23}Al ground state to be J{sup {pi}}=5/2{sup +}. We discuss how this excludes the large increases in the radiative proton capture cross section for the reaction {sup 22}Mg(p,{gamma}){sup 23}Al at astrophysical energies, which were implied by claims that the spin and parity is J{sup {pi}}=1/2{sup +}. The log ft for the Fermi transition to its isobaric analog state (IAS) in {sup 23}Mg 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 {sup 22}Na(p,{gamma}){sup 23}Mg reaction at energies important in novae. The reactions {sup 22}Mg(p,{gamma}){sup 23}Al and {sup 22}Na(p,{gamma}){sup 23}Mg 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 0011cha.
- OSTI ID:
- 20863899
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 74, Issue 4; Other Information: DOI: 10.1103/PhysRevC.74.045810; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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