707 research outputs found
Unified description of fission in fusion and spallation reactions
We present a statistical-model description of fission, in the framework of
compound-nucleus decay, which is found to simultaneously reproduce data from
both heavy-ion-induced fusion reactions and proton-induced spallation reactions
at around 1 GeV. For the spallation reactions, the initial compound-nucleus
population is predicted by the Li\`{e}ge Intranuclear Cascade Model. We are
able to reproduce experimental fission probabilities and fission-fragment mass
distributions in both reactions types with the same parameter sets. However, no
unique parameter set was obtained for the fission probability. The introduction
of fission transients can be offset by an increase of the ratio of
level-density parameters for the saddle-point and ground-state configurations.
Changes to the finite-range fission barriers could be offset by a scaling of
the Bohr-Wheeler decay width as predicted by Kramers. The parameter sets
presented allow accurate prediction of fission probabilities for excitation
energies up to 300 MeV and spins up to 60 \hbar.Comment: 16 pages, 20 figures. Submitted to Phys. Rev.
Isospin dependence of nucleon Correlations in ground state nuclei
The dispersive optical model (DOM) as presently implemented can investigate
the isospin (nucleon asymmetry) dependence of the Hartree-Fock-like potential
relevant for nucleons near the Fermi energy. Data constraints indicate that a
Lane-type potential adequately describes its asymmetry dependence. Correlations
beyond the mean-field can also be described in this framework, but this
requires an extension that treats the non-locality of the Hartree-Fock-like
potential properly. The DOM has therefore been extended to properly describe
ground-state properties of nuclei as a function of nucleon asymmetry in
addition to standard ingredients like elastic nucleon scattering data and level
structure. Predictions of nucleon correlations at larger nucleon asymmetries
can then be made after data at smaller asymmetries constrain the potentials
that represent the nucleon self-energy. A simple extrapolation for Sn isotopes
generates predictions for increasing correlations of minority protons with
increasing neutron number. Such predictions can be investigated by performing
experiments with exotic beams. The predicted neutron properties for the double
closed-shell 132Sn nucleus exhibit similar correlations as those in 208Pb.
Future relevance of these studies for understanding the properties of all
nucleons, including those with high momentum, and the role of three-body forces
in nuclei are briefly discussed. Such an implementation will require a proper
treatment of the non-locality of the imaginary part of the potentials and a
description of high-momentum nucleons as experimentally constrained by the
(e,e'p) reactions performed at Jefferson Lab.Comment: 7 pages and 7 figure
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