Anregung des 7,66 MeV-Niveaus in Kohlenstoff-12 durch unelastische Elektronenstreuung

Using the facilities of the Darmstadt electron linear accelerator the cross section for the excitation of the 7.66 MeV level in Carbon-12 was measured for momentum transfers between 0.25 and 0.55 fm^?1. Extrapolation of the measured cross sections for vanishing momentum transfer yields a partial width for the decay to the ground state through internal pair production of (7.3±1.3)·10^?5 eV. The dependence of the reduced transition probability on momentum transfer is discussed and compared with theoretical predictions.