Neutron physics of the Re/Os clock. I. Measurement of the (n,gamma) cross sections of {sup 186,187,188}Os at the CERN n{sub T}OF facility

• Published in: Physical review. C, Nuclear physics Nuclear physics, 2010-07, Vol.82 (1)
• Main Authors: Mosconi, M., Kaeppeler, F., Audouin, L., Dillmann, I., Heil, M., Plag, R., Voss, F., Walter, S., Wisshak, K., Fujii, K., Abbondanno, U., Belloni, F., Milazzo, P. M., Moreau, C., Mengoni, A., CERN, CH-1211 Geneva, Domingo-Pardo, C., Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia, E-46980 Paterna, Aerts, G., Andriamonje, S., Berthoumieux, E., Dridi, W.
• Format: Article
• Language: English
• Subjects: ABUNDANCE; ALPHA DECAY RADIOISOTOPES; ASTROPHYSICS; BARYON REACTIONS; BARYONS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CAPTURE; CERN; COVERINGS; CROSS SECTIONS; DECAY; DIMENSIONLESS NUMBERS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ENERGY RANGE; EV RANGE; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; EVOLUTION; FERMIONS; GAMMA DECAY; GAMMA RADIATION; HADRON REACTIONS; HADRONS; HEAVY NUCLEI; INTERNATIONAL ORGANIZATIONS; IONIZING RADIATIONS; ISOTOPE RATIO; ISOTOPES; KEV RANGE; MEASURING INSTRUMENTS; NEUTRON REACTIONS; NEUTRONS; NUCLEAR DECAY; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR REACTIONS; NUCLEI; NUCLEON REACTIONS; NUCLEONS; NUCLEOSYNTHESIS; ODD-EVEN NUCLEI; OSMIUM 186; OSMIUM 187; OSMIUM 188; OSMIUM ISOTOPES; PARTICLE DECAY; PHYSICS; RADIATION DETECTORS; RADIATIONS; RADIOISOTOPES; RHENIUM 187; RHENIUM ISOTOPES; S PROCESS; SCINTILLATION COUNTERS; SOLAR SYSTEM; STABLE ISOTOPES; STAR EVOLUTION; SYNTHESIS; TIME-OF-FLIGHT METHOD; YEARS LIVING RADIOISOTOPES
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PHYSREVC.82.015802

The precise determination of the neutron capture cross sections of {sup 186}Os and {sup 187}Os is important to define the s-process abundance of {sup 187}Os at the formation of the solar system. This quantity can be used to evaluate the radiogenic component of the abundance of {sup 187}Os due to the decay of the unstable {sup 187}Re (t{sub 1/2}=41.2 Gyr) and from this to infer the time duration of the nucleosynthesis in our galaxy (Re/Os cosmochronometer). The neutron capture cross sections of {sup 186}Os, {sup 187}Os, and {sup 188}Os have been measured at the CERN n{sub T}OF facility from 1 eV to 1 MeV, covering the entire energy range of astrophysical interest. The measurement has been performed by time-of-flight technique using isotopically enriched samples and two C{sub 6}D{sub 6} scintillation detectors for recording the prompt gamma rays emitted in the capture events. Maxwellian averaged capture cross sections have been determined for thermal energies between kT=5 and 100 keV corresponding to all possible s-process scenarios. The estimated uncertainties for the values at 30 keV are 4.1, 3.3, and 4.7% for {sup 186}Os, {sup 187}Os, and {sup 188}Os, respectively.