J/ApJ/738/143 Ground-state contributions around s-process (Rauscher+, 2011)
Opportunities to constrain astrophysical reaction rates for the s-process via
determination of the ground-state cross-sections.
Rauscher T., Mohr P., Dillmann I., Plag R.
<Astrophys. J., 738, 143 (2011)>
=2011ApJ...738..143R 2011ApJ...738..143R
ADC_Keywords: Atomic physics
Keywords: nuclear reactions - nucleosynthesis - abundances
Abstract:
Modern models of s-process nucleosynthesis in stars require stellar
reaction rates of high precision. Most neutron-capture cross-sections
in the s-process have been measured, and for an increasing number of
reactions the required precision is achieved. This does not
necessarily mean, however, that the stellar rates are constrained
equally well, because only the capture of the ground state of a target
is measured in the laboratory. Captures of excited states can
contribute considerably to stellar rates that are already at typical
s-process temperatures. We show that the ground-state contribution X
to a stellar rate is the relevant measure to identify reactions that
are or could be well constrained by experiments and apply it to
(n,γ) reactions in the s-process. We further show that the
maximum possible reduction in uncertainty of a rate via determination
of the ground-state cross-section is given directly by X. An error
analysis of X is presented, and it is found that X is a robust measure
with mostly small uncertainties. Several specific examples (neutron
capture of 79Se, 95Zr, 121Sn, 187Os, and 193Pt) are
discussed in detail. The ground-state contributions for a set of 412
neutron-capture reactions around the s-process path are presented in a
table. This allows identification of reactions that may be better
constrained by experiments and that cannot be constrained solely by
measuring ground-state cross-sections (and thus require supplementary
studies).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 412 Normalized partition functions G0, ground state
contributions X, their uncertainty factors uX,
and stellar enhancement factors fSEF for nuclides
identified by their charge number Z and mass number A
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See also:
J/MNRAS/418/284 : s-process in low-metallicity stars. II. (Bisterzo+, 2011)
J/MNRAS/404/1529 : s-process in low-metallicity stars (Bisterzo+, 2010)
J/A+A/487/767 : Predictions of nuclear reaction rates (Goriely+, 2008)
J/A+A/441/1195 : Brussels nuclear reaction rate library (Aikawa+, 2005)
http://www.nndc.bnl.gov/ensdf/ : Evaluated Nuclear Structure Data File datasets
retrieval
http://www.kadonis.org/ : Karlsruhe Astrophysical Database of Nucleosynthesis
in Stars home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Z [10/83] Atomic charge number
4- 6 I3 --- A [20/210] Mass number
8- 10 I3 --- --- Repetition of mass number
11- 12 A2 --- Nucl Atome name
14 A1 --- f_Nucl [b] Values given for the ground state (1)
16- 21 F6.3 --- G030 [1/14.53] Normalized partition function at
kT=30keV
23- 27 F5.3 --- X30 [0/1] Ground state contribution at kT=30keV
29- 33 F5.3 --- u30 [1/1.284] Uncertainty factor for X30 (3)
35- 39 F5.3 --- fSEF30 [0.7/1.7] Stellar enhancement factor at kT=30keV
41- 46 F6.3 --- G080 [1/26.69] Normalized partition function at
kT=80keV
48- 52 F5.3 --- X80 [0/1] Ground state contribution at kT=80keV
54- 58 F5.3 --- u80 [1/1.291] Uncertainty factor for X80 (3)
60- 64 F5.3 --- fSEF80 [0.4/1.7] Stellar enhancement factor at kT=80keV
66- 70 A5 --- Com Comment (2)
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Note (1): Flag b: X and fSEF given for the ground state, not the isomeric
state, and assuming thermal equilibration of ground state and excited
states.
Note (2): The marks appearing in the comments refer to KADoNiS v0.3
(Dillmann et al., Proc. EFNUDAT Fast Neutrons-Scientific Workshop
on Neutron Measurements, Theory and Applications, 2009 April 28-30,
Geel, Belgium, ed. Hambsch, available at http://www.kadonis.org/):
n = not present,
t = only theoretical estimate,
30 = only 30keV MACS,
e = measured in the relevant energy range,
* = X30/e_X30<0.8, appearing in Figure 4.
Note (3): uncertainties are negligible for uncertainty factor∼1
See section 2.4 for details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Jan-2013