Angular correlation studies of the Be 9(α, nγ)C 12 reaction

Abstract

Several angular distributions and (n, γ) correlations of the neutron group corresponding to the 4.43 MeV level of C 12, produced in the reaction Be 9(α, nγ)C 12, have been measured using time-of-flight techniques. Bombarding energies of 3.35 MeV and 5.10 MeV were used. Results have been analysed in terms of direct interaction mechanisms. The angular distributions show forward peaking and can be fitted reasonably well by Butler's theory assuming contributions from l = 1 and l = 3 but require a rather large value of the radius parameter. Angular correlation measurements have been done in the reaction plane for neutrons emitted at 10°, 20° and 75° to the direction of the incident beam at energies of 3.35 MeV and 5.10 MeV. These have been fitted by a sum of even order Legendre polynomials. The correlations show marked changes both with neutron angle and bombarding energy, but the symmetry axis is in most cases not very far from the direction of momentum transfer. These results would suggest interference either from different reaction mechanisms, different l-values or both.