Abstract
The weak $r$ process in neutrino-driven winds following a core-collapse supernova is thought to contribute to the cosmic abundances of the first $r$-process peak elements between Se and Ag. Sensitivity studies have found that the early nucleosynthesis in the weak $r$ process is primarily driven by $(\ensuremath{\alpha},xn)$ reactions due to the high temperatures, and that current nuclear physics uncertainties in the $(\ensuremath{\alpha},xn)$ rates result in significant uncertainties of the calculated abundances. The weak $r$-process path proceeds several nuclei away from stability where $(\ensuremath{\alpha},xn)$ reaction cross sections have not yet been measured. In this paper we report the $^{100}\mathrm{Mo}(\ensuremath{\alpha},xn)$ cross section (between 8.9 and 13.2 MeV in the center of mass, corresponding to 3.5--6.8 GK) in inverse kinematics using the Multi-Sampling Ionization Chamber (MUSIC) detector at the Argonne Tandem Linac Accelerator System (ATLAS) facility. With this first measurement of the $^{100}\mathrm{Mo}(\ensuremath{\alpha},xn)$ cross section, we have demonstrated the ability of MUSIC to measure $(\ensuremath{\alpha},xn)$ cross sections for $A$ up to 100, therefore paving the way for further measurements with radioactive beams at ATLAS or the Facility for Rare Isotope Beams.
Submitted Version
Published Version
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