Seminar Details

Measurement of 12C(12C,n)23Mg Deep within the Gamow Window: a Constraint for Weak s-process Nucleosynthesis

Brian Bucher, University of Notre Dame
Thursday, August 15, 11:00 AM - Special Seminar
NSCL Lecture Hall

The 12C(12C,n) reaction (Q=-2.6 MeV) is a potential neutron source for the weak s-process occurring in shell-carbon burning of massive stars. The uncertainty in this reaction rate limits our understanding of the production of elements in the range 60 < A < 90. Current stellar models must rely on the smooth extrapolation of a dubious statistical model calculation based on experimental data which terminates above 3.5 MeV (center-of-mass). Furthermore, the extrapolation cannot account for the resonant structure that should continue to exist at low energies and may contribute a significant rate enhancement at stellar energies. At Notre Dame, this reaction cross section has been measured in finer steps down to 3.1 MeV. The new measurements cover more than two-thirds of the Gamow window for T9=1.1, a typical shell-carbon burning temperature. In addition, a new extrapolation based on measurements of the mirror system has been developed which tries to account for resonances in the excitation function and provides improved agreement with the experimental data. The combination of the recent low-energy measurements with the new extrapolation provides a much tighter constraint on the stellar reaction rate and corresponding nucleosynthesis yields in shell-carbon burning of massive stars.