Session M15: Nuclear Astrophysics II

3:15 PM–4:39 PM, Sunday, April 15, 2007
Hyatt Regency Jacksonville Riverfront Room: City Terrace 11

Chair: Bob Tribble, Texas A&M University

Abstract ID: BAPS.2007.APR.M15.3

Abstract: M15.00003 : The structure of $^{23}$Al and consequences on the depletion of $^{22}$Na from ONe novae

3:39 PM–3:51 PM

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Authors:

Y. Zhai
L. Trache
V.E. Iacob
J.C. Hardy
C. Fu
T. Al-Abdullah
N. Nica
M. McCleskey
V.V. Golovko
H.I. Park
G. Tabacaru
A. Banu
R.E. Tribble
(Texas A\&M University)

There is interest in the structure of $^{23}$Al due to the contribution of the $^{22}$Mg(p, $\gamma )^{23}$Al and $^{22}$Na(p, $\gamma )^{23}$Mg reactions in the depletion of $^{22}$Na from ONe novae. Using MARS we produced and separated pure $^{23}$Al samples with a 48 MeV/u $^{24}$Mg beam from the K500 cyclotron at Texas A{\&}M University. New $\beta$ and $\beta -\gamma$ coincidence measurements were made with a thin scintillator, an HPGe detector and a fast tape transport system. Addition of a BGO Compton shield improved very much the quality of the $\gamma$ spectra around the transitions from the IAS state at 7803 keV. From the measured $\beta$ singles and $\beta -\gamma$ coincidence decay spectra we obtained the $^{23}$Al $\beta$-decay scheme, branching ratios and absolute log\textit{ft} values for several transitions. We clearly determined that the $^{23}$Al ground state spin and parity is J$^{\pi }$=5/2$^{+}$ , not 1/2$^{+}$, and also found spectroscopic information for the states that are resonances in the $^{22}$Na(p, $\gamma )^{23}$Mg reaction. It follows that the larger capture rate implied by the now-rejected lower spin value for $^{23}$Al can not explain the missing 1275 keV cosmic $\gamma$ -ray from the decay of long-lived $^{22}$Na, the last step in the hot NeNa cycle.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.APR.M15.3