New determination of the ${12}C$(alpha,gamma)${16}O$ reaction rate from the gamma-ray angular distribution measurememts

Abstract

The astrophysical reaction rate of the key reaction 12C(alpha,gamma)16O has been determined with the +/- 25% accuracy by two direct experiments at the Stuttgart DYNAMITRON in the framework of a large internatiuonal collaboration. The E1 and E2 capture amplitudes were deduced from 37 new gamma angular distributions in the energy range Ecm = 0.89-2.8 MeV. Highest sensitivity at a picobarn level was reached by using either a close 4pi array of 9 EUROGAM Phase II detectors or the GANDI array of 4 large movable Ge detectors. The S-factor values of the S_E1 and S_E2 excitation functions were calculated by a R-matrix analysis considering also elastic alpha-scattering data and the beta-delayed alpha-decay on 16N