Alpha–alpha potential up to 47.3 MeV bombarding energy

Abstract

Experimental differential cross sections for elastic scattering of two α particles have been fitted with an l-independent non-monotonic real potential up to 34.2 MeV (lab) and a complex potential with non-monotonic real part from 35.1 to 47.3 MeV (lab). The calculated phase shifts, in general, agree with those derived from the phase shift analyses of the experimental cross sections. In particular, the s- and d-wave phase shifts tend to zero in the limit of zero energy implying the absence of any bound state. Thus, ⁸Be is unbound in the potential and the calculated decay width of about 6 eV agrees with the observed one. This potential has its roots in the energy-density functional (EDF) theory with the sudden approximation. In fact, the calculated angular distributions using the derived EDF potential are in reasonable agreement with the experimental data at some energies up to 15.2 MeV (lab). Modifying the Buck, Friedrich and Wheatley (BFW) potential by adding a small repulsive core leads to about the same quality of fits. The modified BFW potential, however, binds ⁸Be in Pauli forbidden states, and s- and d-wave phase shifts in it tend to 2π and π, respectively, in the limit of zero energy.