Beta-delayed proton emission in neutron-deficient lanthanide isotopes

Technical Report · Fri Sep 30 04:00:00 EDT 1988

DOI:https://doi.org/10.2172/6693776· OSTI ID:6693776

Wilmarth, P A

Forty-two ..beta..-delayed proton precursors with 56less than or equal toZless than or equal to71 and 63less than or equal toNless than or equal to83 were produced in heavy-ion reactions at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decay properties studied at the on-line mass separation facility OASIS. Twenty-five isotopes and eight delayed proton branches were identified for the first time. Delayed proton energy spectra and proton coincident ..gamma..-ray and x-ray spectra were measured for all precursors. In a few cases, proton branching ratios were also determined. The precursor mass numbers were determined by the separator, while the proton coincident x-ray energies provided unambiguous Z identifications. The proton coincident ..gamma..-ray intensities were used to extract final state branching ratios. Proton emission from ground and isomeric states was observed in many cases. The majority of the delayed proton spectra exhibited the smooth bell-shaped distribution expected for heavy mass precursors. The experimental results were compared to statistical model calculations using standard parameter sets. Calculations using Nilsson model/RPA ..beta..-strength functions were found to reproduce the spectral shapes and branching ratios better than calculations using either constant or gross theory ..beta..-strength functions. Precursor half-life predictions from the Nilsson model/RPA ..beta..-strength functions were also in better agreement with the measured half-lives than were gross theory predictions. The ratios of positron coincident proton intensities to total proton intensities were used to determine Q/sub EC/-B/sub p/ values for several precursors near N=82. The statistical model calculations were not able to reproduce the experimental results for N=81 precursors. 154 refs., 82 figs., 19 tabs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6693776
• Report Number(s): LBL-26101; ON: DE89003038
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BRANCHING RATIO
CHARGED-PARTICLE REACTIONS
DATA ACQUISITION SYSTEMS
DECAY
DETECTION
HEAVY ION REACTIONS
ISOTOPES
MATHEMATICAL MODELS
NUCLEAR DECAY
NUCLEAR MODELS
NUCLEAR REACTIONS
PROTON EMISSION DECAY
PROTON SPECTRA
SHELL MODELS
SPECTRA
STATISTICAL MODELS