scholarly journals s-Processing in Asymptotic Giant Branch Stars in the Light of Revised Neutron-Capture Cross Sections

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 239
Author(s):  
Diego Vescovi ◽  
René Reifarth
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Reaction Rates ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Capture Cross ◽  
Magnetic Buoyancy ◽  
Stellar Models ◽  
Pocket Formation ◽  
Capture Cross Sections

Current AGB stellar models provide an adequate description of the s-process nucleosynthesis that occurs. Nonetheless, they still suffer from many uncertainties related to the modeling of the 13C pocket formation and the adopted nuclear reaction rates. For many important s-process isotopes, a best set of neutron-capture cross sections was recently re-evaluated. Using stellar models prescribing that the 13C pocket is a by-product of magnetic-buoyancy-induced mixing phenomena, s-process calculations were carried out with this database. Significant effects are found for a few s-only and branching point isotopes, pointing out the need for improved neutron-capture cross section measurements at low energy.

scholarly journals Neutron Capture Cross Sections for the Weak s Process

2009 ◽  
Vol 26 (3) ◽  
pp. 243-249 ◽  
Author(s):  
M. Heil ◽  
A. Juseviciute ◽  
F. Käppeler ◽  
R. Gallino ◽  
M. Pignatari ◽  
...  
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Nuclear Data ◽  
Mass Range ◽  
Asymptotic Giant Branch ◽  
Capture Cross ◽  
Medium Mass ◽  
Spectroscopic Information ◽  
Process Component ◽  
Capture Cross Sections

AbstractIn past decades a lot of progress has been made towards understanding the main s-process component that takes place in thermally pulsing Asymptotic Giant Branch (AGB) stars. During this process about half of the heavy elements, mainly between 90 ≤ A ≤ 209 are synthesized. Improvements were made in stellar modeling as well as in measuring relevant nuclear data for a better description of the main s process. The weak s process, which contributes to the production of lighter nuclei in the mass range 56 ≤ A ≤ 90 operates in massive stars (M ≥ 8 M⊙) and is much less understood. A better characterization of the weak s component would help disentangle the various contributions to element production in this region. For this purpose, a series of measurements of neutron-capture cross sections have been performed on medium-mass nuclei at the 3.7-MV Van de Graaff accelerator at FZK using the activation method. Also, neutron captures on abundant light elements with A < 56 play an important role for s-process nucleosynthesis, since they act as neutron poisons and affect the stellar neutron balance. New results are presented for the (n, γ) cross sections of 41K and 45Sc, and revisions are reported for a number of cross sections based on improved spectroscopic information.

scholarly journals THE IMPACT OF UPDATED Zr NEUTRON-CAPTURE CROSS SECTIONS AND NEW ASYMPTOTIC GIANT BRANCH MODELS ON OUR UNDERSTANDING OF THESPROCESS AND THE ORIGIN OF STARDUST

2013 ◽  
Vol 780 (1) ◽  
pp. 95 ◽  
Author(s):  
Maria Lugaro ◽  
Giuseppe Tagliente ◽  
Amanda I. Karakas ◽  
Paolo M. Milazzo ◽  
Franz Käppeler ◽  
...  
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Asymptotic Giant Branch ◽  
Capture Cross ◽  
The Impact ◽  
Capture Cross Sections

scholarly journals Galactic Ba Enrichment from TP-AGB Stars

1993 ◽  
Vol 155 ◽  
pp. 580-580
Author(s):  
C. M. Raiteri ◽  
M. Busso ◽  
F. Matteucci ◽  
R. Gallino
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Nuclear Physics ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Capture Cross ◽  
Strong Indication ◽  
Low Mass ◽  
Neutron Exposure ◽  
Capture Cross Sections

The production of the bulk of barium has long been ascribed to the main component of the s-process, whose astrophysical site has been envisaged in the convective He shell of Thermally Pulsing Asymptotic Giant Branch (TP-AGB) stars of low mass (1–3 M⊙; see Käppeler et al. 1990). The main neutron source is the 13C(α, n)16O reaction, operating at the thermal energy of kT = 12keV. We have calculated neutron captures in such environment with an updated nuclear physics, adopting the neutron capture cross sections of Beer, Voß, & Winters (1992) together with their temperature-dependence. Stellar models producing a mean neutron exposure of τ0 ≃ 0.30 mb−1 are able to reproduce the solar distribution of the s-abundances satisfactory, but the Ba isotopes show some overproduction. Such a strong indication suggests a revision of the Ba cross sections (see Gallino, Raiteri, & Busso 1992). Once that a suitable choice of σn, γ(Ba) is made, it is found that a r-contribution to solar Ba of the order of 10% can be expected.

THERMAL NEUTRON CAPTURE CROSS-SECTION OF Na23 AND Mn55

1953 ◽  
Vol 31 (3) ◽  
pp. 204-206 ◽  
Author(s):  
Rosalie M. Bartholomew ◽  
R. C. Hawkings ◽  
W. F. Merritt ◽  
L. Yaffe
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Cross Sections ◽  
Neutron Capture ◽  
Half Life ◽  
Capture Cross Section ◽  
Thermal Neutron Capture ◽  
Capture Cross ◽  
Neutron Capture Cross Section ◽  
Capture Cross Sections

The thermal neutron capture cross sections of Na23 and Mn55 have been determined using the activation method. The values are 0.53 ± 0.03 and 12.7 ± 0.3 barns respectively with respect to σAul97 = 93 barns. These agree well with recent pile oscillator results. The half-life for Mn56 is found to be 2.576 ± 0.002 hr.

Neutron capture cross-sections by comparative γ-activation

1986 ◽  
Vol 13 (5) ◽  
pp. 287-288 ◽  
Author(s):  
H.S. Sahota ◽  
V.K. Mittal ◽  
N.P.S. Sidhu
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Capture Cross ◽  
Capture Cross Sections

scholarly journals Determining neutron capture cross sections via the surrogate reaction technique

2007 ◽  
Vol 75 (5) ◽  
Author(s):  
C. Forssén ◽  
F. S. Dietrich ◽  
J. Escher ◽  
R. D. Hoffman ◽  
K. Kelley
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
Capture Cross ◽  
Capture Cross Sections
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