Statistical and non statistical models for delayed neutron emission: applications to nuclei near A = 90
A detailed analysis of the simple statistical model description for delayed neutron emission of /sup 87/Br, /sup 137/I, /sup 85/As and /sup 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 /sup 87/Br. For /sup 85/As and /sup 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 /sup 87/Br and /sup 91/ /sup 93/ /sup 95/ /sup 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 /sup 84/ /sup 86/As, /sup 86/ /sup 92/Br and /sup 88/ /sup 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 gross theory of ..beta..-decay, we find that structures in the tail of the Gamow-Teller giant resonances are expected which strongly influence the decay properties of nuclides in this region.
- Research Organization:
- California Univ., Berkeley (USA)
- OSTI ID:
- 6143002
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANTIMONY 135
BETA DECAY
DELAYED NEUTRONS
ARSENIC ISOTOPES
BROMINE ISOTOPES
IODINE 137
NEUTRON EMISSION
STATISTICAL MODELS
RUBIDIUM ISOTOPES
GAMOW-TELLER RULES
SHELL MODELS
STRENGTH FUNCTIONS
THEORETICAL DATA
ALKALI METAL ISOTOPES
ANTIMONY ISOTOPES
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DATA
DECAY
ELEMENTARY PARTICLES
EMISSION
FERMIONS
FISSION NEUTRONS
FUNCTIONS
HADRONS
INFORMATION
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MATHEMATICAL MODELS
NEUTRONS
NUCLEAR MODELS
NUCLEI
NUCLEONS
NUMERICAL DATA
ODD-EVEN NUCLEI
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
651712* - Nuclear Properties & Reactions
A=90-149
Theoretical- Radioactive Decay- (-1987)
653005 - Nuclear Theory- Radioactive Decay