| A detailed analysis of the simple statistical model description for delayed neutron emission of ('87)Br, ('137)I, ('85)As and ('135)Sb has been performed. In agreement with experimental findings, structure in the (beta)-strength function is required to reproduce the envelope of the neutron spectrum from ('87)Br. For ('85)As and ('135)Sb the model is found incapable of simultaneously reproducing envelopes of delayed neutron spectra and neutron branching ratios to excited states in the final nuclei for any choice of (beta)-strength function. The results indicate that partial widths for neutron emission are not compatible with optical-model transmission coefficients.;The simple shell model with pairing is shown to qualitatively describe the main features of the (beta)-strength functions for decay of ('87)Br and ('91,93,95,97)Rb. It is found that the location of apparent resonances in the experimental data are in rough agreement with the location of centroids of strength calculated with this model.;An extension of the shell model picture which includes the Gamow-Teller residual interaction is used to investigate decay properties of ('84-86)As, ('86-92)Br and ('88-102)Rb. For a realistic choice of interaction strength, the half lives of these isotopes are fairly well reproduced and semiquantitative agreement with experimental (beta)-strength functions is found. Delayed neutron emission probabilities are reproduced for precursors nearer stability with systematic deviations being observed for the heavier nuclei.(').;Contrary to the assumption of a structureless Gamow-Teller giant resonance as embodied in the gross theory of (beta)-decay, we find that structures in the tail of the Gamow-Teller giant resonance are expected which strongly influence the decay properties of nuclides in this region. |
