New measurement of neutron capture resonances in {sup 209}Bi
- Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia (Spain)
- Istituto Nazionale di Fisica Nucleare, Trieste (Italy)
- CEA/Saclay-DSM, Gif-sur-Yvette (France)
- Universidade de Santiago de Compostela (Spain)
- Centro de Investigaciones Energeticas Medioambientales y Technologicas, Madrid (Spain)
The neutron capture cross section of {sup 209}Bi has been measured at the CERN n{sub T}OF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Additional experimental sources of systematic error, such as the electronic threshold in the detectors, summing of {gamma}-rays, internal electron conversion, and the isomeric state in bismuth, have been taken into account. {gamma}-Ray absorption effects inside the sample have been corrected by employing a nonpolynomial weighting function. Because {sup 209}Bi is the last stable isotope in the reaction path of the stellar s-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by {alpha} decays. In the relevant stellar range of thermal energies between kT=5 and 8 keV our new capture rate is about 16% higher than the presently accepted value used for nucleosynthesis calculations. At this low temperature an important part of the heavy Pb-Bi isotopes are supposed to be synthesized by the s-process in the He shells of low mass, thermally pulsing asymptotic giant branch stars. With the improved set of cross sections we obtain an s-process fraction of 19{+-}3% of the solar bismuth abundance, resulting in an r-process residual of 81{+-}3%. The present (n,{gamma}) cross-section measurement is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.
- OSTI ID:
- 20863755
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 74, Issue 2; Other Information: DOI: 10.1103/PhysRevC.74.025807; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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