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Title: Radius-of-curvature of the S factor maximum in sub-barrier fusion hindrance.

Abstract

A maximum of the S(E) factor is evidence for an onset of sub-barrier fusion hindrance and it can be well described by a radius-of-curvature expression near the maximum. The systematics of this radius of curvature has been studied over a wide range of projectile-target combinations. It follows a tentative general trend as a function of the parameter {zeta}=Z{sub 1}Z{sub 2}{radical}({mu}), and is strongly affected by effects associated with the nuclear structure of the nuclei in the entrance channel. It also explains the reason why the S factor maximum is not easily recognized visually for lighter, astrophysically interesting fusion systems.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
914988
Report Number(s):
ANL/PHY/JA-58894
Journal ID: ISSN 0556-2813; PRVCAN; TRN: US0804867
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. C; Journal Volume: 75; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR STRUCTURE; NUCLEI; ANL

Citation Formats

Jiang, C. L., Back, B. B., Janssens, R. V. F., Rehm, K. E., and Physics. Radius-of-curvature of the S factor maximum in sub-barrier fusion hindrance.. United States: N. p., 2007. Web. doi:10.1103/PhysRevC.75.057604.
Jiang, C. L., Back, B. B., Janssens, R. V. F., Rehm, K. E., & Physics. Radius-of-curvature of the S factor maximum in sub-barrier fusion hindrance.. United States. doi:10.1103/PhysRevC.75.057604.
Jiang, C. L., Back, B. B., Janssens, R. V. F., Rehm, K. E., and Physics. Mon . "Radius-of-curvature of the S factor maximum in sub-barrier fusion hindrance.". United States. doi:10.1103/PhysRevC.75.057604.
@article{osti_914988,
title = {Radius-of-curvature of the S factor maximum in sub-barrier fusion hindrance.},
author = {Jiang, C. L. and Back, B. B. and Janssens, R. V. F. and Rehm, K. E. and Physics},
abstractNote = {A maximum of the S(E) factor is evidence for an onset of sub-barrier fusion hindrance and it can be well described by a radius-of-curvature expression near the maximum. The systematics of this radius of curvature has been studied over a wide range of projectile-target combinations. It follows a tentative general trend as a function of the parameter {zeta}=Z{sub 1}Z{sub 2}{radical}({mu}), and is strongly affected by effects associated with the nuclear structure of the nuclei in the entrance channel. It also explains the reason why the S factor maximum is not easily recognized visually for lighter, astrophysically interesting fusion systems.},
doi = {10.1103/PhysRevC.75.057604},
journal = {Phys. Rev. C},
number = 2007,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A maximum of the S(E) factor is evidence for an onset of sub-barrier fusion hindrance and it can be well described by a radius-of-curvature expression near the maximum. The systematics of this radius of curvature has been studied over a wide range of projectile-target combinations. It follows a tentative general trend as a function of the parameter {zeta}=Z{sub 1}Z{sub 2}{radical}({mu}), and is strongly affected by effects associated with the nuclear structure of the nuclei in the entrance channel. It also explains the reason why the S factor maximum is not easily recognized visually for lighter, astrophysically interesting fusion systems.
  • Recent fusion reaction data for the systems {sup 36}S+{sup 48}Ca, {sup 48}Ca+{sup 48}Ca, and {sup 96}Zr+{sup 48}Ca are analyzed within the coupled-channel formalism. The heavy-ion entrance channel potential is calculated employing an improved double-folding prescription. The nonlocal kernel arising from the knock-on exchange component of the effective N-N interaction is localized within the lowest order of the Perey-Saxon approach, including full recoil. The single-particle densities entering the folding integrals are prescribed according to the density matrix expansion method. The investigation is more elaborated because each case is tested with four different types of N-N effective forces: The two standard parametrizationsmore » of the density-independent M3Y force (Reid and Paris) and two parametrizations of the density-dependent Gogny force (D1S and D1N). A consistent description of all three reactions is achieved by keeping fixed the nuclear structure input for {sup 48}Ca. The inclusion of 2{sup +} and 3{sup -} phonon states in the coupled-channel calculation, within an energy excitation window identical for all three reactions explains better the hindrance in extreme sub-barrier fusion cross sections. The interactions providing the best fit to the data are not pointing to a possible maximum in the astrophysical S factor, thereby confirming the conclusion reached by the Legnaro group for these cases.« less
  • No abstract prepared.
  • The recent discovery of hindrance in heavy-ion induced fusion reactions at extreme sub-barrier energies represents a challenge for theoretical models. Previously, it has been shown that in medium-heavy systems, the onset of fusion hindrance depends strongly on the 'stiffness' of the nuclei in the entrance channel. In this work, we explore its dependence on the total mass and the Q-value of the fusing systems and find that the fusion hindrance depends in a systematic way on the entrance channel properties over a wide range of systems.
  • The excitation function for the fusion-evaporation reaction {sup 64}Ni+{sup 100}Mo has been measured down to a cross section of {approx}5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep falloff of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at E{sub s}=120.6 MeV, which corresponds to 90% of the reference energy E{sub s}{sup ref}, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactionsmore » leading to compound nuclei with mass A=100-200 is presented in order to explore a possible dependence of fusion hindrance on nuclear structure.« less