α-particle spectrum in the reaction p + 11B → α + 8Be* → 3α

Using a simple phenomenological parametrization of the reaction amplitude we calculated α -particle spectrumin the reaction p + 11 B → α + 8 Be* → 3 α at the resonance proton energy of 675 keV. The parametrization includes Breit-Wigner factor with an energy-dependent width for intermediate 8 Be* state and the Coulomb and the centrifugal factors in α -particle-emission vertices. The shape of the spectrum consists of a well-defined peak corresponding to emission of the primary α and a flat shoulder going down to very low energy. We found that below 1.5MeV there are 17.5% of α ’s and below 1MeV there are 11% of them.