Physics – Nuclear Physics
Scientific paper
Nov 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phrvc..50.2582v&link_type=abstract
Physical Review C (Nuclear Physics), Volume 50, Issue 5, November 1994, pp.2582-2601
Physics
Nuclear Physics
39
Radiative Capture, 90<=A<=149, Stellar Structure, Interiors, Evolution, Nucleosynthesis, Ages, Origin, Formation, And Abundances Of The Elements
Scientific paper
The neutron capture cross sections of 134Ba, 135Ba, 136Ba, and 137Ba were measured in the energy range from 5 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7Li (p,n)7 Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4π barium fluoride detector. The cross section ratios were determined with an overall uncertainty of ~3%, an improvement by factors of 5 to 8 compared to existing data. Severe discrepancies were found with respect to previous results. As a new possibility in time of flight experiments, isomeric cross section ratios could be determined for 135Ba, 136Ba, and 137Ba. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=10 keV and 100 keV. These stellar cross sections were used in an s-process analysis. For the s-only isotopes 134Ba and 136Ba the Ns<σ> ratio was determined to 0.875+/-0.025. Hence, a significant branching of the s-process path at 134Cs can be claimed for the first time, in contrast to predictions from the classical approach. This branching yields information on the s-process temperature, indicating values around T8=2. The new cross sections are also important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Together with the results from previous experiments on tellurium and samarium, a general improvement of the Ns<σ> systematics in the mass range A=120-150 is achieved. This yields a more reliable separation of s- and r-process contributions for comparison with stellar observations, but reveals a 20% discrepancy with respect to the solar barium abundance.
Guber K.
Käppeler Franz
Reffo G.
Voss Florian
Wisshak K.
No associations
LandOfFree
Stellar neutron capture cross sections of the Ba isotopes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Stellar neutron capture cross sections of the Ba isotopes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stellar neutron capture cross sections of the Ba isotopes will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-950010