The reaction ${}^{141}$Pr($\alpha ,n$)${}^{144}$Pm was investigated between $E_{\alpha }=$ 11 MeV and 15 MeV with the activation method using the $\gamma \gamma$ coincidence method with a segmented clover-type high-purity Germanium (HPGe) detector. Measurements with four other HPGe detectors were additionally made. The comparison proves that the $\gamma \gamma$ coincidence method is an excellent tool to investigate cross sections down to the microbarn range. The ($\alpha ,n$) reaction at low energy is especially suited to test $\alpha +\text{nucleus}$ optical-model potentials for application in the astrophysical $p$ process. The experimentally determined cross sections were compared to Hauser-Feshbach statistical model calculations using different optical potentials and generally an unsatisfactory reproduction of the data was found. A local potential was constructed to improve the description of the data. The consequences of applying the same potential to calculate astrophysical ($\gamma ,\alpha$) rates for ${}^{145}$Pm and ${}^{148}$Gd were explored. In summary, the data and further results underline the problems in global predictions of $\alpha +\text{nucleus}$ optical potentials at astrophysically relevant energies.

• Received 29 July 2011

DOI:https://doi.org/10.1103/PhysRevC.84.045808