Application of Nuclear Reaction Models for Neutron Nuclear Data Evaluation: Statistical and Optical Model Calculations for <sup>134–138</sup>Ba

Strohmaier, B.; Uhl, M.; Matthes, W.

doi:10.13182/nse78-a27164

Cited by 10 publications

(4 citation statements)

References 41 publications

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“…[39] and additional information camefrom Refs. [40][41]. These data sets were modified until the total cross sections of Table 5 could be reproduced within their uncertainties and the capture cross sections within ""1 0%.…”

Section: O"i(x) = Zi(x) I;z(au) I;e(x) Rn(aumentioning

confidence: 99%

Stellar neutron capture cross sections of the Ba isotopes

et al. 1994

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The neutron capture cross sections of 134 Ba, 135 Ba, 136 Ba, and 137 Ba 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 7 Li(p,nfBe reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 47r Barium Fluoride Detector. Several runs have been performed under different experimental conditions to study the systematic uncertainties, which resulted mainly from the large ratios of total to capture cross sections of up to 400. The cross section ratios were determined with an overall uncertainty of "'3%, an improvement by factors of five to eight compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 10 ke V and 100 ke V. These stellar cross sections were used in an s-process analysis. For the s-only isotopes 134 Ba and 136 Ba the Nsratio was determined to 0.875±0.025. Hence, a significant brauehing of the s-process path at 134 Cs can be claimed for the first time, in cantrast to predictions from the classical approach. This brauehing yields information on the s-process temperature, indicating values araund T 8 = 2. The new cross sections arealso important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Tagether with the results from previous experiments on tellurium and samarium, a general improvement of the Nssystematics in the mass range A = 120 to 150 is achieved. This allows for a more reliable separation of s-and r-process yields, resulting in an improved assignment of the respective contributions to eiemental barium that is required for comparison with stellar observations. ZUSAMMENFASSUNG

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Section: O"i(x) = Zi(x) I;z(au) I;e(x) Rn(aumentioning

confidence: 99%

Stellar neutron capture cross sections of the Ba isotopes

et al. 1994

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“…It must be a nucleon and no distinction is made between neutrons and protons. The rate of PE emission can be controlled by the input parameter F M, which is connected to the average effective matrix element M of the residual interaction [11]:…”

Section: Pre-equilibrium Processesmentioning

confidence: 99%

“…On the other hand quite a few powerful models and associated codes were developed for particle induced reactions. A very popular one is the computer code STAPRE [11]. It combines the model of Hauser-Feshbach (HF) [12] and the exciton model in Griffin's original formulation.…”

Section: Introductionmentioning

confidence: 99%

The role of angular-momentum removal in photonuclear reactions as deduced from the isomeric ratios for and

Kolev

Ernst

1998

J. Phys. G: Nucl. Part. Phys.

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A model interpretation of isomeric ratios for 117m,g In and 120m,g Sb produced in the reactions 118 Sn(γ , p), 119 Sn(γ , np), 121 Sb(γ , α), nat Sb(γ , α2n), 121 Sb(γ , n) and nat Sb(γ , 3n) is presented. The experimental isomeric ratios were obtained using bremsstrahlung radiation with end-point energies of 18 and 43 MeV. The calculations were performed by means of the well known code STAPRE and the new code COMPLET. Angular-momentum removal in preequilibrium emission was found to be much more important for the observed isomeric ratios than subsequent compound-nucleus evaporation.

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“…Using for all isotopes R'=~gsR}=5.45fm [2], as described in the introduction, the resonance scattering lengths for the isotopes are obtained as b, (fm) = b -5.52…”

Section: Ba-isotopesmentioning

confidence: 99%

Neutron scattering lengths and cross sections of the barium isotopes

1985

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Coherent neutron scattering lengths and total cross sections have been measured for barium compounds and on isotopically enriched samples for neutron energies from 0.5meV up to 132eV using different techniques. From the experimental data the following quantities were obtained: -the coherent scattering lengths (in fro) of Ba (5.07_+0.03) and of the isotopes with mass numbers 130 (-3.6+_0.6); 132 (7.8_+0.3); 134 (5.7_+0.1); 135 (4.66_+0.10); 136 (4.90 +_0.08); 137 (6.82+0.10); and 138 (4.83 +_0.08). -the absorption cross sections o-s (at 0.025 eV in barn): of Ba (1.1_+0.1) and of the isotopes: 130 (30_+5); 136 (0.68+_0:17); 137 (3.6+_0.2); and 138 (0.27 +_0.14).-zero-energy scattering cross sections for Ba and the isotopes 136, 137 and 138. On the basis of these data, the isotopic-and spin-incoherent cross sections and the (s)resonance contributions to the coherent scattering lengths have been determined and discussed.

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Application of Nuclear Reaction Models for Neutron Nuclear Data Evaluation: Statistical and Optical Model Calculations for ^134–138Ba

Cited by 10 publications

References 41 publications

Stellar neutron capture cross sections of the Ba isotopes

Stellar neutron capture cross sections of the Ba isotopes

The role of angular-momentum removal in photonuclear reactions as deduced from the isomeric ratios for and

Neutron scattering lengths and cross sections of the barium isotopes

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Application of Nuclear Reaction Models for Neutron Nuclear Data Evaluation: Statistical and Optical Model Calculations for 134–138Ba

Cited by 10 publications

References 41 publications

Stellar neutron capture cross sections of the Ba isotopes

Stellar neutron capture cross sections of the Ba isotopes

The role of angular-momentum removal in photonuclear reactions as deduced from the isomeric ratios for and

Neutron scattering lengths and cross sections of the barium isotopes

Contact Info

Product

Resources

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Application of Nuclear Reaction Models for Neutron Nuclear Data Evaluation: Statistical and Optical Model Calculations for ^134–138Ba