Program - Brookhaven National Laboratory

PR 120
Coupled-Channel Models of Direct+Semidirect Capture via Giant-Dipole Resonances
Ian J. Thompson, Jutta E. Escher, Livermore National Laboratory L-414, Livermore CA 945551. Goran
Arbanas, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6171.
It was recognized in the 1970’s that semidirect capture, a two-step process that excites a giant-dipole
resonance in the first step, followed by its radiative de-excitation in the second step, is a dominant process
near giant-dipole resonances in the neutron energy range 5–20 MeV. At lower energies such processes
may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We therefore
implemented a semidirect capture in a coupled-channel code FRESCO [1] and validated it by computing
direct-semidirect capture 208 Pb(n,γ) 209 Pb into the ground and excited states of 209 Pb for which experimental
data exist [2]. We use a conventional single-particle direct-semidirect capture code CUPIDO [3,4]
for comparisons. Furthermore, we present and discuss our computations of direct+semidirect capture cross
section 130 Sn(n,γ) 131 Sn [5] whose effect on nucleosynthesis models is known to be large [6]. Prepared by
LLNL under Contract DE-AC52-07NA27344, through the topical collaboration TORUS.
[1] I.J. Thompson, Computer Physics Reports, 7, 167, (1988). [2] I. Bergqvist et al., Nucl. Phys., A191,
641 (1972), S. Joly et al., A382, 71 (1982). [3] W.E. Parker et al., Phys. Rev. C52, 252 (1995); [4] F.S.
Dietrich, private communication [5] R. L. Kozub et al., submitted to Phys. Rev. Lett. (2012). [6] R.
Surman et al., Phys. Rev. C79, 045809 (2009).
PR 121
Using R-matrix Parameters to Describe One-Nucleon Transfers to Resonances
Ian J. Thompson, Jutta E. Escher,, Livermore Laboratory L-414, Livermore CA 94551. Akram M.
Mukhamedzhanov, Texas A & M Laboratory, College Station TX 77843.
Deuteron-induced reactions, in particular (d,p) one-neutron transfer reactions, have been used for decades
to investigate the structure of nuclei. These reactions, carried out in inverse kinematics, will play a central
role in the study of weakly-bound systems at modern radioactive beam facilities. While the theoretical
framework and its computational implementation for describing (d,p) reactions have seen much progress
over the decades, open questions remain and need to be addressed, including the proper treatment of
transfers to resonance states. Recently, Mukhamedzhanov [1] proposed a novel approach that describes
transfers to both bound and resonance states. The new formalism, which is general enough to include
deuteron breakup, formulates the cross section in terms of a dominant surface term that can be expressed
in terms of R-matrix parameters. Here we test some of the ideas underlying the proposed formalism,
compare calculations to measured cross sections, and discuss implications. Prepared by LLNL under
Contract DE-AC52-07NA27344, through the topical collaboration TORUS.
[1] A. Mukhamedzhanov, PRC 84, 044616 (2011)
PR 122
Isospin-dependent Microscopic Nucleon Optical Potential within Relativistic Brueckner
Hartree-Fock Framework
Ruirui Xu, Zhongyu Ma, China Institute of Atomic Energy. E. N. E. van Dalen, H. Müther, Institut für
Theoretische Physik, Universität Tübingen.
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