6533b854fe1ef96bd12ade39

RESEARCH PRODUCT

Investigation of beta strength functions by neutron and gamma-ray spectroscopy

subject

description

Abstract Neutron spectra from the decay of the β− delayed neutron precursors 55.6 sec 87Br, 24.5 sec 137I, 2.05 sec 85As and 1.71 sec 135Sb have been studied with high resolution 3He ionization chambers. By γ-ray measurements, the partial neutron emission probabilities to excited states in 84Se and 134Te have been determined independently. For the neutron-emitter nuclei 87Kr and 137Xe, from which neutron decay proceeds only to the ground states of the final nuclei, 86Kr and 136Xe, unique information on the shape of the β− strength function Sβ(E) is obtained. For the emitter nuclei 85Se and 135Te, correlations between neutron transition energies and differences in level energies in 84Se and 134Te, have defined some levels in 85Se and 135Te which are strongly fed by β− decay. It is shown that the experimental shape of the β− strength function cannot be explained by the widely used assumptions Sβ(E) = const or Sβ(E) ∼ ϱ(E) or by the “gross theory” of β-decay, but that it is the result of structures in the low-energy tail of the Gamow-Teller giant resonance (GTGR) expected from general nuclear structure considerations.