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ABSTRACT: A microscopic calculation of reaction cross sections for nucleon-nucleus
scattering has been performed by explicitly coupling the elastic channel to all
particle-hole excitations in the target and one-nucleon pickup channels. The
particle-hole states may be regarded as doorway states through which the flux
flows to more complicated configurations, and subsequently to long-lived
compound nucleus resonances. Target excitations for $^{40,48}$Ca, $^{58}$Ni,
$^{90}$Zr and $^{144}$Sm were described in a random-phase framework using a
Skyrme functional. Reaction cross sections obtained agree very well with
experimental data and predictions of a state-of-the-art fitted optical
potential. Couplings between inelastic states were found to be negligible,
while the pickup channels contribute significantly. The effect of resonances
from higher-order channels was assessed. Elastic angular distributions were
also calculated within the same method, achieving good agreement with
experimental data. For the first time observed absorptions are completely
accounted for by explicit channel coupling, for incident energies between 10
and 70 MeV, with consistent angular distribution results.
Phys. Rev. C. 10/2011; 84(6).
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ABSTRACT: A microscopic calculation of reaction cross sections for nucleon-nucleus scattering was performed by coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for (40,48)Ca, 58Ni, 90Zr, and 144Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agreed very well with experimental data and predictions of a fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. For the first time observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 40 MeV.
Physical Review Letters 11/2010; 105(20):202502. · 7.37 Impact Factor
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ABSTRACT: A microscopic calculation of the optical potential for nucleon-nucleus
scattering has been performed by explicitly coupling the elastic channel to all
the particle-hole (p-h) excitation states in the target and to all relevant
pickup channels. These p-h states may be regarded as doorway states through
which the flux flows to more complicated configurations, and to long-lived
compound nucleus resonances. We calculated the reaction cross sections for the
nucleon induced reactions on the targets $^{40,48}$Ca, $^{58}$Ni, $^{90}$Zr and
$^{144}$Sm using the QRPA description of target excitations, coupling to all
inelastic open channels, and coupling to all transfer channels corresponding to
the formation of a deuteron. The results of such calculations were compared to
predictions of a well-established optical potential and with experimental data,
reaching very good agreement. The inclusion of couplings to pickup channels
were an important contribution to the absorption. For the first time,
calculations of excitations account for all of the observed reaction
cross-sections, at least for incident energies above 10 MeV.
07/2010;
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ABSTRACT: A microscopic calculation of the reaction cross-section for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole (p-h) excitation states in the target and to all one-nucleon pickup channels. The p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for 40,48Ca, 58Ni, 90Zr and 144Sm were described in a QRPA framework using a Skyrme functional. Reaction cross sections calculated in this approach were compared to predictions of a fitted optical potential and to experimental data, reaching very good agreement. Couplings between inelastic states were found to be negligible, while the couplings to pickup channels contribute significantly. For the first time observed reaction cross-sections are completely accounted for by explicit channel coupling, for incident energies between 10 and 40 MeV. Comment: Accepted for publication on Physical Review Letters. Article is expected to be published in the November 12, 2010 issue. 4 pages, 4 figures
06/2010;
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ABSTRACT: The prospects for determining cross sections for compound-nuclear neutron-capture reactions from Surrogate measurements are investigated. Calculations as well as experimental results are presented that test the Weisskopf-Ewing approximation, which is employed in most analyses of Surrogate data. It is concluded that, in general, one has to go beyond this approximation in order to obtain (n,γ) cross sections of sufficient accuracy for most astrophysical and nuclear-energy applications.
EPJ Web of Conferences. 01/2010;
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ABSTRACT: We study the spin-parity distribution P(J$^{\pi}$,E) of $^{156}$Gd excited states above the neutron separation energy that are expected to be populated via the neutron pickup reaction $^{157}$Gd($^{3}$He,$^{4}$He)$^{156}$Gd. In general, modeling of the spin-parity distribution is important for the applicability of the surrogate reaction technique as a method of deducing reaction cross sections. We model excited states in $^{156}$Gd as rotational states built on intrinsic states consisting of a hole in the core where the hole represents neutron removal form a deformed single particle state. The reaction cross section to each excited state is calculated using standard reaction code that uses spherical reaction form-factor input. The spectroscopic factor associated with each form-factor is the expansion coefficient of the deformed neutron state in a spherical Sturmian basis consisting of the spherical reaction form-factors.
07/2007;
