Stellar (<i>n</i>,γ) cross section of the unstable isotope<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Eu</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>155</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>

Jaag, S.; Käppeler, F.

doi:10.1103/physrevc.51.3465

Cited by 27 publications

(10 citation statements)

References 12 publications

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“…The only cross section measurements on radioactive branching points in the mass region of interest here were measured for 147 Pm [10] and for 155 Eu [11] by means of the activation technique. Since the activation technique can not be applied for the determination of the 151 Sm cross section, all previous branching analyses had to resort to theoretical values for this important isotope.…”

Section: Introductionmentioning

confidence: 99%

Stellar neutron capture cross section of the unstables-process branching pointSm151

Wisshak¹,

Voß²,

Käppeler³

et al. 2006

Phys. Rev. C

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The neutron capture cross sections of the radioactive isotope 151 Sm and of natural samarium have been measured in the energy range from 3 keV to 225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the 7 Li(p, n) 7 Be reaction by bombarding metallic Li targets with a pulsed proton beam and capture events were registered with the Karlsruhe 4π Barium Fluoride Detector. The cross sections were determined relative to the gold standard using a 206 mg sample of samarium oxide with 90% enrichment in 151 Sm. Over most of the measured energy range uncertainties of ∼2-3% could be achieved for the 151 Sm/ 197 Au ratio. Maxwellian averaged neutron capture cross sections of 151 Sm were calculated for thermal energies between kT = 8 keV and 100 keV with due consideration of the stellar enhancement factor and were found to be systematically larger than all previous theoretical predictions used in the analysis of the s-process branching at 151 Sm. In the context of the branching analysis, an experimental determination of the stellar enhancement factor due to captures in thermally excited states is proposed, and the tentative determination of the p-process residual of 152 Gd and a few other cases is discussed.

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Section: Introductionmentioning

confidence: 99%

Stellar neutron capture cross section of the unstables-process branching pointSm151

Wisshak¹,

Voß²,

Käppeler³

et al. 2006

Phys. Rev. C

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“…Those are of special interest, because instead of β decay an additional neutron capture may occur and lead to a branching of the process path. For those branching points neutron capture cross sections can only be measured directly in some special cases due to the difficulties with dealing with an unstable target [5], [6], [7]. These experiments showed deviations up to 50% regarding to recommended values based on [8].…”

Section: Motivationmentioning

confidence: 99%

Nuclear Astrophysics with Tagged Photons

Schnorrenberger

Lindenberg²,

Pietralla³

et al. 2009

Proceedings of 10th Symposium on Nuclei in the Cosmos — PoS(NIC X)

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For the modeling of the astrophysical s-process the knowledge of neutron capture cross sections is crucial. Where experimental data is not available for the (n,γ) cross-section like e.g. short-lived branching points, the observation of the inverse (γ,n) reaction can provide useful information -in particular, if the cross section can be measured as a function of energy. The NEPTUN tagger setup at the S-DALINAC delivers a suited tagged photon beam (6-20MeV).In a first test run the resolution turned out to be 35 keV which is close to NEPTUN's design specifications.10th Symposium on Nuclei in the Cosmos

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“…30 ) For example, a measurement of the 155Eu cross section (t 1 / 2 =4.96 yr) could be performed with a sample of only 88 ng corresponding to 304x 10 14 atoms, a must for minimizing the sample activity to a manageable level. 31 ) Another, more recent measurement of the (n,'Y) cross section of an unstable branch point was carried out on 147Pm, which is important for understanding the neutron density at the stellar site of the s process. 32 ) In this case, some 147Pm was added to a solution of enriched 147Sm (98.27%) which served as a carrier.…”

Section: Activation In a Quasi-stellar Neutron Spectrum (1) Experimenmentioning

confidence: 99%

Neutron Capture at keV Energies - Probing the Stellar Interior

Käppeler¹,

Arlandini²,

Heil³

et al. 2002

Journal of Nuclear Science and Technology

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Neutron capture nucleosynthesis, which is producing essentially all elements between Fe and the actinides, takes place in the He burning zones of evolved stars (8 process) and presumably in supernovae (r process). The slow time scale of stellar burning scenarios implies that the associated neutron capture path follows the stability valley and that the resulting abundances are to good approximation inversely proportional to the respective (n,,),) cross sections. The experimental program at the Karlsruhe Van de Graaff accelerator, which is focused on this field, includes time-of-flight measurements with a 47r BaF2 array, activations in a quasi-stellar neutron spectrum, and complementing studies of important a-induced reactions. Recent examples will be presented for each of these areas to illustrate the actual status as well as the need for further efforts. The consequences of these laboratory results for deriving constraints on the physical parameters of the He burning zones are discussed at the example of the stellar neutron flux.

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Stellar (n,γ) cross section of the unstable isotopeEu155

Cited by 27 publications

References 12 publications

Stellar neutron capture cross section of the unstables-process branching pointSm151

Stellar neutron capture cross section of the unstables-process branching pointSm151

Nuclear Astrophysics with Tagged Photons

Neutron Capture at keV Energies - Probing the Stellar Interior

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