Precise measurement of the thermal and stellar $^{54}$Fe($n, \gamma$)$^{55}$Fe cross sections via AMS

Anton Wallner, Tamas Belgya, Kathrin Buczak, Laurent Coquard, Max Bichler, Iris Dillmann, Robin Golser, Franz Käppeler, Amanda Karakas, Walter Kutschera, Claudia Lederer, Alberto Mengoni, Marco Pignatari, Alfred Priller, Rene Reifarth, Peter Steier, Laszlo Szentmiklosi, Claudia Lederer

Research output: Contribution to journalArticlepeer-review

Abstract

The detection of long-lived radionuclides through ultra-sensitive single atom counting via accelerator mass spectrometry (AMS) offers opportunities for precise measurements of neutron capture cross sections, e.g. for nuclear astrophysics. The technique represents a truly complementary approach, completely independent of previous experimental methods. The potential of this technique is highlighted at the example of the $^{54}$Fe($n, \gamma$)$^{55}$Fe reaction. Following a series of irradiations with neutrons from cold and thermal to keV energies, the produced long-lived $^{55}$Fe nuclei ($t_{1/2}=2.744(9)$ yr) were analyzed at the Vienna Environmental Research Accelerator (VERA). A reproducibility of about 1% could be achieved for the detection of $^{55}$Fe, yielding cross section uncertainties of less than 3%. Thus, the new data can serve as anchor points to time-of-flight experiments. We report significantly improved neutron capture cross sections at thermal energy ($\sigma_{th}=2.30\pm0.07$ b) as well as for a quasi-Maxwellian spectrum of $kT=25$ keV ($\sigma=30.3\pm1.2$ mb) and for $E_n=481\pm53$ keV ($\sigma= 6.01\pm0.23$ mb). The new experimental cross sections have been used to deduce improved Maxwellian average cross sections in the temperature regime of the common $s$-process scenarios. The astrophysical impact is discussed using stellar models for low-mass AGB stars.
Original languageEnglish
Pages (from-to)25808
JournalPhysical Review C
Volume96
Issue number2
DOIs
Publication statusPublished - 28 Aug 2017

Keywords

  • Nuclear Experiment
  • Astrophysics - Solar and Stellar Astrophysics

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