The ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O reaction is one of the most important in nuclear astrophysics since it determines the ratio of ${}^{12}$C to ${}^{16}$O during stellar helium burning. Experimental data, however, are still subject to large uncertainties due to the almost vanishing cross section at stellar energies. So far, most measurements have been performed with germanium detectors. To compensate for their low efficiency, the highest beam currents had to be used, resulting in target degradation and beam-induced backgrounds. Instead, the present measurement was performed with high-efficiency detectors and low beam currents, using the Karlsruhe 4$\pi$ BaF${}_2$ detector and the pulsed 3.7-MV Van de Graaff accelerator at Karlsruhe Institute of Technology. The ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O cross sections have been measured at center-of-mass energies $E$ between 1002 and 1510 keV, and the $E1$ and $E2$ components were derived with an accuracy comparable to the previous best data obtained with HPGe detectors.

• Received 5 March 2012

DOI:https://doi.org/10.1103/PhysRevC.86.015805