Neutron angular distributions from the Be 9(α, n)C 12 reaction at 14.1, 13.9 and 13.5 MeV

Abstract

The angular distributions of the neutrons to the ground state and the first, second, third and fourth excited states of C 12 from the Be 9(α, n)C 12 reaction have been measured with the time-of-flight technique at three different α-energies, viz.14.1 ± 0.1 MeV, 13.9 ± 0.1 MeV and 13.5 ± 0.1 MeV. The ground state and the first and second excited state groups could be resolved at all angles, while the third and the fourth excited state groups had to be separated by use of the known shapeof the broad 10.1 MeV group 1). The measurement at 14.1 MeV has been reported earlier 2) and the reason for repeating the measurement as a slightly different bombarding energy was pointed out in that work: the excitation energy in C 13 for an α-energy of 14.1 MeV corresponds closely to a level at 20.5 MeV which might increase the probability for compound nucleus formation relative to a direct reaction at this α-energy.