The reaction Be 9(He 3, n)C 11 from 1.3 to 5.4 MeV

Abstract

Excitation functions of Be 9(He 3, n 0)C 11 and Be 9(He 3, n 1)C 11∗ at θ lab = 0°, 90° and 160° were measured in the energy range of 1.30 MeV to 4.90 MeV He 3 bombarding energy. The excitation functions for the two groups are similar in shape and show only very broad structure. Angular distributions were measured for both neutron groups at 1.59, 1.77, 1.97, 2.19, 2.48, 2.80, 3.11, 3.46, 3.81, 4.12, 4.52, 4.90 and 5.35 MeV He 3 bombarding energies. Analysis of the angular distributions in terms of Legendre polynomials, together with other evidence, indicates that a level is formed in the C 12 compound nucleus with a width of several hundred kilovolts at an excitation energy of 27.8 MeV. These angular distributions show strong changes in shape with increasing energy. For the ground state group, the angular distribution changes from near symmetry about 90° to strong peaking at 0° as the energy increases. The first excited state group changes from a weak to a strong backward peak, then to forward and backward peaking and, finally, to dominant forward peaking as the energy increases. An interpretation in terms of double stripping is given for the higher energy ground state angular distributions.