Abstract
Background: Uncertainties in adopted models of optical-model potentials directly influence the accuracy in the theoretical predictions of reaction rates as they are needed for reaction-network calculations in, for instance, -process nucleosynthesis. The improvement of the optical-model potential is hampered by the lack of experimental data at astrophysically relevant energies especially for heavier nuclei.
Purpose: Measuring the reaction cross section at sub-Coulomb energies extends the scarce experimental data available in this mass region and helps understanding the energy dependence of the imaginary part of the optical-model potential at low energies.
Method: Applying the activation method, after the irradiation of natural rhenium targets with -particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the reaction cross section were determined via -ray spectroscopy by using the Cologne Clover Counting Setup and the method of coincidences.
Results: Cross-section values at five energies close to the astrophysically relevant energy region were measured. Statistical model calculations revealed discrepancies between the experimental values and predictions based on widely used +nucleus optical-model potentials. However, an excellent reproduction of the measured cross-section values could be achieved from calculations based on the so-called Sauerwein–Rauscher optical-model potential.
Conclusion: The results obtained indicate that the energy dependence of the imaginary part of the optical-model potential can be described by an exponential decrease. Successful reproductions of measured cross sections at low energies for -induced reactions in the mass range confirm the global character of the Sauerwein–Rauscher potential.
1 More- Received 15 September 2014
- Revised 21 November 2014
DOI:https://doi.org/10.1103/PhysRevC.90.065807
©2014 American Physical Society