Abstract
Thermal neutron capture -ray spectra for and have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and enriched targets. Complete neutron capture -ray decay schemes for the () reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the -ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV ray from () was measured as and the thermal neutron cross section for this ray was determined as mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose -ray cross sections were previously standardized. The -ray cross sections for the () and () reactions were then determined relative to the 870.76-keV -ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the -ray cross sections and transition probabilities; mb; mb; mb; and mb.
- Received 8 October 2015
- Revised 18 February 2016
DOI:https://doi.org/10.1103/PhysRevC.93.044311
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