C-12(alpha,gamma)O-16: The key reaction in stellar nucleosynthesis

The angular distributions of gamma rays from the C-12(alpha, gamma)O-16 rea ction have been measured at 20 energy points in the energy range E-cm = 0.9 5 to 2.8 MeV. The sensitivity of the present experiment compared to previou s direct investigations was raised by 1-2 orders of magnitude, by using an array of highly efficient (100%) Ge detectors shielded actively with BGOs, as well as high beam currents of up to 500 muA that were provided by the St uttgart DYNAMITRON accelerator. The SE1 and SE2 factors deduced from the ga mma angular distributions have been extrapolated to the range of helium bur ning temperatures applying the R-matrix method, which yielded S-E1(300) = ( 76 +/- 20) keV b and S-E2(300) = (85 +/- 30) keV b.