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Title: New measurements of the {sup 19}F(n,{gamma}){sup 20}F cross section and their implications for the stellar reaction rate

Abstract

The puzzle concerning the nucleosynthetic origin of {sup 19}F has been a topic of much interest in astrophysics. After the observation of an overabundance of {sup 19}F in thermally pulsing asymptotic giant branch (AGB) stars, attention has been drawn to the He shell flash, characteristic of these stars, as a possible site of fluorine synthesis. As the He intershell of AGBs is also known to undergo periods of high neutron exposure, {sup 19}F synthesized in this zone would be in danger of destruction by {sup 19}F(n,{gamma}){sup 20}F. The current recommended value of the Maxwellian averaged cross section (MACS) is uncertain by 20% in a temperature region corresponding to the He flash, which is insufficient for accurate stellar modeling. A measurement of the cross section has been performed at the Karlsruhe 3.7 MV Van de Graaff accelerator by cyclic activation of fluorine samples in a quasistellar neutron spectrum with a mean thermal energy of kT=25 keV. The new MACS at kT=25 keV is 44% lower and six times more accurate than reported previously.

Authors:
 [1];  [2]; ;  [1]; ;  [3]
  1. Forschungszentrum Karlsruhe, Institut fuer Kernphysik, D-76021 Karlsruhe (Germany)
  2. (United States)
  3. University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556 (United States)
Publication Date:
OSTI Identifier:
20995168
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.035801; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ASTROPHYSICS; CROSS SECTIONS; CURRENTS; FLUORINE; FLUORINE 19; FLUORINE 20; KEV RANGE 10-100; NEUTRON SPECTRA; NEUTRONS; REACTION KINETICS; STARS; VAN DE GRAAFF ACCELERATORS

Citation Formats

Uberseder, Ethan, University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556, Heil, Michael, Kaeppeler, Franz, Goerres, Joachim, and Wiescher, Michael. New measurements of the {sup 19}F(n,{gamma}){sup 20}F cross section and their implications for the stellar reaction rate. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.035801.
Uberseder, Ethan, University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556, Heil, Michael, Kaeppeler, Franz, Goerres, Joachim, & Wiescher, Michael. New measurements of the {sup 19}F(n,{gamma}){sup 20}F cross section and their implications for the stellar reaction rate. United States. doi:10.1103/PHYSREVC.75.035801.
Uberseder, Ethan, University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556, Heil, Michael, Kaeppeler, Franz, Goerres, Joachim, and Wiescher, Michael. Thu . "New measurements of the {sup 19}F(n,{gamma}){sup 20}F cross section and their implications for the stellar reaction rate". United States. doi:10.1103/PHYSREVC.75.035801.
@article{osti_20995168,
title = {New measurements of the {sup 19}F(n,{gamma}){sup 20}F cross section and their implications for the stellar reaction rate},
author = {Uberseder, Ethan and University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556 and Heil, Michael and Kaeppeler, Franz and Goerres, Joachim and Wiescher, Michael},
abstractNote = {The puzzle concerning the nucleosynthetic origin of {sup 19}F has been a topic of much interest in astrophysics. After the observation of an overabundance of {sup 19}F in thermally pulsing asymptotic giant branch (AGB) stars, attention has been drawn to the He shell flash, characteristic of these stars, as a possible site of fluorine synthesis. As the He intershell of AGBs is also known to undergo periods of high neutron exposure, {sup 19}F synthesized in this zone would be in danger of destruction by {sup 19}F(n,{gamma}){sup 20}F. The current recommended value of the Maxwellian averaged cross section (MACS) is uncertain by 20% in a temperature region corresponding to the He flash, which is insufficient for accurate stellar modeling. A measurement of the cross section has been performed at the Karlsruhe 3.7 MV Van de Graaff accelerator by cyclic activation of fluorine samples in a quasistellar neutron spectrum with a mean thermal energy of kT=25 keV. The new MACS at kT=25 keV is 44% lower and six times more accurate than reported previously.},
doi = {10.1103/PHYSREVC.75.035801},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}