Prospects for Surrogate Neutron Capture
Measurements with Radioactive Ion
Beams and GODDESS
Jolie A. Cizewski, Andrew Ratkiewicz, Alexandre Lepailleur, Steven D. Pain,
Heather Garland, Harrison Sims, and David Walter
1 Introduction
The neutron capture (n,γ) reaction is responsible for the synthesis of almost all of
the elements heavier than iron. The slow s-process proceeds close to the line of
nuclear stability. In contrast, waiting points for the rapid neutron capture r-process
are very neutron-rich isotopes far from stability. Reproducing the observed r-process
abundance pattern is a sensitive measure of the astrophysical r-process site(s) and
requires knowledge of the properties of and (n,γ) reaction rates on isotopes near the
waiting points, nuclei far from stability and with very short half-lives [1].
Understanding (n,γ) rates near the r-process path is especially challenging because this reaction cannot be measured directly, because short-lived
(t 1/2 < <100 days) targets cannot be manufactured and the lack of a pure neutron
target for studies with radioactive ion beams. Near the N = 82 shell closure at
132 Sn, neutron capture is dominated by direct-semi-direct (DSD) capture that
depends sensitively on the excitation energies and spectroscopic factors of the 3p 1/2
and 3p 3/2 neutron configurations. These properties have been measured [2–4] in
(d,p) reactions with radioactive ion beams of 132,130,128,126 Sn and the DSD capture
cross sections as a function of neutron energy have been deduced [3, 4]. While the
J. A. Cizewski () · A. Lepailleur · H. Garland · H. Sims · D. Walter
Rutgers University, New Brunswick, NJ, USA
e-mail: cizewski@physics.rutgers.edu
A. Ratkiewicz
Rutgers University, New Brunswick, NJ, USA
Lawrence Livermore National Laboratory, Livermore, CA, USA
S. D. Pain
Oak Ridge National Laboratory, Oak Ridge, TN, USA
© This is a U.S. government work and not under copyright protection
in the U.S.; foreign copyright protection may apply 2021
J. Escher et al. (eds.), Compound-Nuclear Reactions, Springer Proceedings in
Physics 254, https://doi.org/10.1007/978-3-030-58082-7_26
217
Measurements with Radioactive Ion
Beams and GODDESS
Jolie A. Cizewski, Andrew Ratkiewicz, Alexandre Lepailleur, Steven D. Pain,
Heather Garland, Harrison Sims, and David Walter
1 Introduction
The neutron capture (n,γ) reaction is responsible for the synthesis of almost all of
the elements heavier than iron. The slow s-process proceeds close to the line of
nuclear stability. In contrast, waiting points for the rapid neutron capture r-process
are very neutron-rich isotopes far from stability. Reproducing the observed r-process
abundance pattern is a sensitive measure of the astrophysical r-process site(s) and
requires knowledge of the properties of and (n,γ) reaction rates on isotopes near the
waiting points, nuclei far from stability and with very short half-lives [1].
Understanding (n,γ) rates near the r-process path is especially challenging because this reaction cannot be measured directly, because short-lived
(t 1/2 < <100 days) targets cannot be manufactured and the lack of a pure neutron
target for studies with radioactive ion beams. Near the N = 82 shell closure at
132 Sn, neutron capture is dominated by direct-semi-direct (DSD) capture that
depends sensitively on the excitation energies and spectroscopic factors of the 3p 1/2
and 3p 3/2 neutron configurations. These properties have been measured [2–4] in
(d,p) reactions with radioactive ion beams of 132,130,128,126 Sn and the DSD capture
cross sections as a function of neutron energy have been deduced [3, 4]. While the
J. A. Cizewski () · A. Lepailleur · H. Garland · H. Sims · D. Walter
Rutgers University, New Brunswick, NJ, USA
e-mail: cizewski@physics.rutgers.edu
A. Ratkiewicz
Rutgers University, New Brunswick, NJ, USA
Lawrence Livermore National Laboratory, Livermore, CA, USA
S. D. Pain
Oak Ridge National Laboratory, Oak Ridge, TN, USA
© This is a U.S. government work and not under copyright protection
in the U.S.; foreign copyright protection may apply 2021
J. Escher et al. (eds.), Compound-Nuclear Reactions, Springer Proceedings in
Physics 254, https://doi.org/10.1007/978-3-030-58082-7_26
217