Determination of 141 Pr( α , n ) 144 Pm cross sections at energies of relevance for the astrophysical p process using the γ γ coincidence method

The reaction ${}^{141}$Pr($\\ensuremath{\\alpha},\\phantom{\\rule{-0.16em}{0ex}}n$)${}^{144}$Pm was investigated between ${E}_{\\ensuremath{\\alpha}}=$ 11 MeV and 15 MeV with the activation method using the $\\ensuremath{\\gamma}\\ensuremath{\\gamma}$ 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 $\\ensuremath{\\gamma}\\ensuremath{\\gamma}$ coincidence method is an excellent tool to investigate cross sections down to the microbarn range. The ($\\ensuremath{\\alpha},\\phantom{\\rule{-0.16em}{0ex}}n$) reaction at low energy is especially suited to test $\\ensuremath{\\alpha}+\\text{nucleus}$ 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 ($\\ensuremath{\\gamma},\\ensuremath{\\alpha}$) rates for ${}^{145}$Pm and ${}^{148}$Gd were explored. In summary, the data and further results underline the problems in global predictions of $\\ensuremath{\\alpha}+\\text{nucleus}$ optical potentials at astrophysically relevant energies.