Nucleosynthesis and Neutron-Capture Cross Sections

Allen, Barry J.; Gibbons, John H.; Macklin, R. L.

doi:10.1007/978-1-4615-8228-1_4

Cited by 104 publications

(43 citation statements)

References 54 publications

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“…[18]. Figure 1 shows a comparison of our experimental total capture cross-sections with σ 30 values derived with various theoretical models [28,29,30,31,32,24,23,20] In the case of 130 Ba our experimental value agrees with the measurement of ref. [27].…”

Section: 25supporting

confidence: 81%

(n, γ) cross-sections of light p nuclei

Dillmann

Heil²,

Käppeler³

et al.

The 2nd International Conference on Nuclear Physics in Astrophysics

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Abstract. The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and is thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called "p process". So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n, γ) activation measurements on p nuclei, related by detailed balance to the respective photodisintegrations, was carried out at the Karlsruhe Van de Graaff accelerator using the 7 Li(p, n) 7 Be source for simulating a Maxwellian neutron distribution of kT = 25 keV. We present here preliminary results of our extended measuring program in the mass range between A = 74 and A = 132, including first experimental (n, γ)

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Section: 25supporting

confidence: 81%

(n, γ) cross-sections of light p nuclei

Dillmann

Heil²,

Käppeler³

et al.

The 2nd International Conference on Nuclear Physics in Astrophysics

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“…The comparison with previous recommendations [45,46], experimental data [41,47], and theoretical predictions [17,19,[48][49][50] is summarized in Table XV for the MACS at kT = 30 keV.…”

Section: Comparison Of 30 Kev Macs With Previous Datamentioning

confidence: 76%

Stellar(n,γ)cross sections ofp-process isotopes Part I:
Dillmann
¹
,
Domingo‐Pardo
²
,
Heil
³

et al. 2010
Phys. Rev. C
23
1
19
0
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We have investigated the (n, γ) cross sections of p-process isotopes with the activation technique. The measurements were carried out at the Karlsruhe Van de Graaff accelerator using the 7 Li(p, n)7 Be source for simulating a Maxwellian neutron distribution of kT = 25 keV. I. INTRODUCTIONAstrophysical models can explain the origin of most nuclei beyond the iron group by a combination of processes involving neutron captures on long (s-process) or short (r-process) time scales [1,2].However, 32 proton-rich stable isotopes between 74 Se and 196 Hg cannot be formed in these neutron capture processes, because they are either shielded by stable isotopes from the r-process decay chains or lie outside the s-process flow (Fig. 1). These isotopes, which are ascribed to the so-called "p-process", are 10 to 100 times less abundant than their s-and r-process neighbors. So far, the astrophysical site of the p-process is still under discussion, since the solar p-abundances can not be completely described by current models.Historically, the p-process was thought to proceed via proton captures, but a plausible site with the required amount of free protons could not be identified. Moreover, elements with large Z cannot be produced by proton captures because the temperatures necessary to overcome * Electronic address: iris.dillmann@ph. the Coulomb repulsion favor photodisintegration rather than charged-particle capture.The most plausible astrophysical site is the explosively burning Ne/O layer in core collapse supernovae, which is heated to ignition temperatures by the outgoing shock front [3][4][5]. In this high-temperature environment proton-rich nuclei are produced by sequences of photodissociations and β + decays. In stars 20 times more massive than the sun the p-process temperatures for efficient photo-disintegration are already reached at the end of hydrostatic Ne/O burning [6]. This mechanism is also called "γ process" because proton-rich isotopes are produced by (γ, n) reactions on pre-existing seed nuclei from

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“…Stellar neutron capture cross sections have first been compiled in 1971 by Allen et al (1971), who presented a set of recommended (n, γ) cross sections averaged over a Maxwell-Boltzmann distribution for a thermal energy of kT = 30 keV. This first collection of Maxwellian averaged cross sections (MACS) comprised already 130 experimental cross sections with typical uncertainties between 10 and 25%.…”

Section: Compilations Of Stellar (N γ) Cross Sections and Further Rementioning

confidence: 99%

Thesprocess: Nuclear physics, stellar models, and observations

et al. 2011

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Nucleosynthesis in the s process takes place in the He burning layers of low mass AGB stars and during the He and C burning phases of massive stars. The s process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting s-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the s-process reaction network, current models are aiming at ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear and atomic physics, and stellar modeling is reviewed and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the sprocess path. The strong variations of the s-process efficiency with metallicity bear also interesting consequences for Galactic chemical evolution.

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Nucleosynthesis and Neutron-Capture Cross Sections

Cited by 104 publications

References 54 publications

(n, γ) cross-sections of light p nuclei

(n, γ) cross-sections of light p nuclei

Stellar(n,γ)cross sections ofp-process isotopes Part I:
Dillmann
¹
,
Domingo‐Pardo
²
,
Heil
³

et al. 2010
Phys. Rev. C
23
1
19
0
View full text Add to dashboard Cite

Thesprocess: Nuclear physics, stellar models, and observations

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Nucleosynthesis and Neutron-Capture Cross Sections

Cited by 104 publications

References 54 publications

(n, γ) cross-sections of light p nuclei

(n, γ) cross-sections of light p nuclei

Stellar(n,γ)cross sections ofp-process isotopes Part I:Dillmann1, Domingo‐Pardo2, Heil3 et al. 2010Phys. Rev. C231190View full textAdd to dashboardCite

Thesprocess: Nuclear physics, stellar models, and observations

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Stellar(n,γ)cross sections ofp-process isotopes Part I:
Dillmann
¹
,
Domingo‐Pardo
²
,
Heil
³

et al. 2010
Phys. Rev. C
23
1
19
0
View full text Add to dashboard Cite