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