A High-Precision Determination of the Astrophysical Rate for Production of $^{9}$Be
ORAL
Abstract
New cross section measurements of the astrophysically important $^{9}$Be($\gamma$,n) reaction have been made from 1.5 to 5.18 MeV. The measurements were made using the nearly monoenergetic circularly polarized $\gamma$-ray beam at Triangle Universities Nuclear Laboratory's High Intensity $\gamma$-ray Source. Measurements over narrow resonances employed beams with energy spread dE/E $\leq$ 1\%. The energy-dependent absolute efficiency of the neutron counter used in this work was measured to $\pm$ 3\% accuracy. New resonance parameters for the 4 lowest lying states in $^{9}$Be were determined. A new reaction rate for $\alpha + \alpha + n$ has been determined to better than $\pm$ 5\%. The present rate is $\sim$ 25\% larger than two widely accepted rates [1-2] in the temperature range important for r-process nucleosynthesis. The implications of this new rate on r-process and nuclear abundance predictions will be discussed.\\[4pt] [1] C. Angulo \textit{et al.} Nuc. Phys. A 656 (1999) 3-183. \\[0pt] [2] K. Sumiyoshi \textit{et al.} Nuc. Phys A 709 (2002) 467-486.
*Work supported in part by USDOE Office of Nuclear Physics Grants DE-FG02-97ER41041 and DE-FG02-97ER41033.
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