Abstract
Photoneutron energy spectra from the reaction were measured as functions of laboratory angle over a range of excitation energies from 30 to 35 MeV. Angular distribution Legendre-polynomial coefficients were extracted up to third order as functions of excitation energy. Nonzero values of the coefficients and were observed over the energy region explored, indicating interference between states of opposite parity. These values can be accounted for in a simple model incorporating electric quadrupole absorption strength decaying via the ground-state photoneutron channel. When combined with the previously-determined amplitude ratio for the and single-particle transitions, the present results suggest that about 4% of the isovector energy-weighted sum rule is found in the (,) channel in the energy range studied. The value of the (,) cross section was found to vary from 1.5±0.1 mb at MeV to 0.8±0.1 mb at 35 MeV. The average magnitude of the contribution to this cross section was estimated to be 0.05±0.02 mb. This is in reasonable agreement with a recent continuum randomphase approximation shell model calculation, but is in disagreement with a previous measurement.
- Received 6 February 1984
DOI:https://doi.org/10.1103/PhysRevC.30.1789
©1984 American Physical Society