Program - Brookhaven National Laboratory

in inverse kinematics. I will present the measurement of (γ, n) reactions at the LAND/R3B setup at GSI
Darmstadt, focussing on the recent development of the high resolution fast neutron detector NeuLAND.
This detection system will allow measurements of the (γ, n) channel with unprecedented accuracy and
thus provide important information about neutron capture cross section on radioactive species in the
astrophysically interesting energy regime.
PR 5
Nuclear Data Processing and Dissemination Efforts for Nuclear Astrophysics at ORNL
Caroline D. Nesaraja, Michael S. Smith, Physics Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee, 37831. USA. Eric J. Lingerfelt, Computer Science and Mathematics Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee, 37831. USA.
At research facilities around the world, nuclear astrophysics measurements are being made with radioactive
and stable beams to enhance our understanding of the evolution and explosion of stars and their creation
of elements. For these extensive data to be effectively used in astrophysical simulations, they must be
evaluated, processed, and disseminated to the community. As the amount of data acquired in this field increases,
there have been efforts to streamline these processes. One example is an online software system, the
Computational Infrastructure for Nuclear Astrophysics (CINA). Utilized by researchers in 126 institutions
and 29 countries, CINA can generate thermonuclear reaction rates from nuclear data input, incorporate
rates into libraries, and run and visualize astrophysics simulations with these libraries. CINA, freely available
online at nucastrodata.org, consists of a suite of codes which provide data processing, management,
visualization, and dissemination capabilities, as well as workflow management. We will describe some of
these features of CINA with examples of reaction rate calculations, simulations, and disseminations.
PR 6
Low Level Densities of Exotic 131,133 Sn Isotopes and Impact on r-process Nucleosynthesis
Shi-Sheng Zhang, School of Physics and Nuclear Energy Engineering, Beihang Univ., Beijing, China.
M.S. Smith, Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. G. Arbanas,
Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. R.L.
Kozub, Dept. of Physics, Tennessee Technological Univ., Cookeville, TN, USA.
Neutron capture rates on unstable nuclei near the doubly-magic exotic 132 Sn were recently shown to
significantly impact the synthesis of heavy elements in the r-process in supernovae [1]. These rates are
usually determined from cross sections estimated with statistical models employing a Fermi gas level
density formulation. Such an approach is only valid if the density of levels in the compound nucleus is
sufficiently high. We examine the validity of this assumption for neutron capture on 130,132 Sn by making
self-consistent calculations of single-particle bound and resonant levels in 131,133 Sn using the analytical
continuation of the coupling constant (ACCC) based on a relativistic mean field (RMF) theory with BCS
approximation. Knowledge of bound states with a strong single particle nature can be used to calculate
direct neutron capture, and information on single particle resonances above the neutron capture threshold
can be used to determine the level density for statistical models – as well as to calculate capture into
individual resonances. Our RMF+ACC+BCS model predicts four strong single-particle bound levels in
both 131,133 Sn with an ordering that agrees with recent transfer reaction experiments [2,3] and spacings
that, while differing from experiment, are consistent between the Sn isotopes. In 131 Sn and 133 Sn, we also
find at most one single-particle level in the effective energy range for neutron captures in the r-process
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