Photoneutron angular distributions for 32S

Abstract

Angular distributions of the energy spectra of photoneutrons emitted in the reaction 32S(γ, n0)31S were measured over the range of excitation energies from 18 to 29 MeV. Coefficients of Legendre polynomials fitted to the data gave no indication of photon absorption other than through electric dipole transitions, except at energies above 27 MeV. The measured value of the normalized Legendre coefficient a2 is − 1.0 ± 0.1 across most of the giant resonance region supports a simple shell model interpretation that the 2s12 → 2p32 single-particle transition (of channel spin 0) is the dominant mechanism for photoabsorption followed by neutron decay to the ground state of 31S. Comparison of the present results for the ground state channel with the total photoneutron cross section shows that up to an excitation energy of 18.5 MeV nearly all neutron-emitting transitions proceed to the ground state of 31S even though many channels for excited states are open. The ground state photoneutron channel exhausts about 6% of the TRK sum rule.