Importance of isovector effects in reproducing neutron total cross section differences in the W isotopes

Dietrich, Frank; Anderson, J. D.; Bauer, R.; Grimes, S. M.; Finlay, R.W.; Abfalterer, Werner; Bateman, Fred; Haight, R. C.; Morgan, G. L.; Bauge, E.; Delaroche, J. P.; Romain, P.

doi:10.1103/physrevc.67.044606

Cited by 26 publications

(22 citation statements)

References 38 publications

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“…1. The experimental data was shifted up by +0.002, well within the estimated uncertainty of the vertical scale (0.02) [4], arising from uncertainties in the areal densities of the uranium and thorium targets. The measurements are well reproduced by the axial rigid-rotor DCCOM potential calculations with the present optical potential parameters from Table I.…”

Section: Resultssupporting

confidence: 60%

“…It is generally accepted that differences of neutron total cross sections among neighboring nuclei provide an unusually stringent test of optical models [1][2][3][4]. At the same time it has been shown that the standard optical model treatment fails to reproduce the observed differences of total cross sections both for tungsten isotopes [4] and Th-U nuclei [5].…”

Section: Introductionmentioning

confidence: 99%

“…At the same time it has been shown that the standard optical model treatment fails to reproduce the observed differences of total cross sections both for tungsten isotopes [4] and Th-U nuclei [5]. Based on these findings it was stated that the prediction of the global optical model potential for actinides with A 232 still needs extensive experimental and theoretical investigations [5].…”

Section: Introductionmentioning

confidence: 99%

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Is a global coupled-channel dispersive optical model potential for actinides feasible?

et al. 2005

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An isospin-dependent coupled-channel optical model potential containing a dispersive term with a nonlocal contribution is used to simultaneously fit the available experimental database (including strength functions and scattering radius) for neutron and proton scattering on strongly deformed 238 U and 232 Th nuclei. The energy range 0.001-200 MeV is covered. A dispersive coupled-channel optical model (DCCOM) potential with parameters that show a smooth energy dependence and energy-independent geometry are determined from fits to the entire data set. Calculations using the obtained DCCOM potential reproduce measured total cross-section differences between 232 Th and 238 U within experimental uncertainty. The isovector terms and the observed very weak dependence of the geometrical parameters on mass number A allow us to extend the derived potential parameters to neighboring actinide nuclei with great confidence.

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Section: Resultssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Is a global coupled-channel dispersive optical model potential for actinides feasible?

et al. 2005

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“…It is generally accepted that differences of neutron total cross sections among neighboring nuclei provide an unusually stringent test of optical models [88][89][90][91]. At the same time it has been shown that the standard optical-model treatment fails to reproduce the observed differences of total cross sections for tungsten isotopes [88]; incident neutron energies below 5 MeV are especially challenging owing to the increasing impact of the target nuclear structure on calculated cross sections.…”

Section: Resultsmentioning

confidence: 99%

Nucleon scattering on actinides using a dispersive optical model with extended couplings

et al. 2016

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The Tamura coupling model [Rev. Mod. Phys. 37, 679 (1965)] has been extended to consider the coupling of additional low-lying rotational bands to the ground-state band. Rotational bands are built on vibrational bandheads (even-even targets) or single-particle bandheads (odd-A targets) including both axial and nonaxial deformations. These additional excitations are introduced as a perturbation to the underlying axially symmetric rigid-rotor structure of the ground-state rotational band. Coupling matrix elements of the generalized optical model are derived for extended multiband transitions in even-even and odd-A nuclei. Isospin symmetric formulation of the optical model is employed. A coupled-channels optical-model potential (OMP) containing a dispersive contribution is used to fit simultaneously all available optical experimental databases including neutron strength functions for nucleon scattering on 232 Th, 233,235,238 U, and 239 Pu nuclei. Quasielastic (p,n) scattering data on 232 Th and 238 U to the isobaric analog states of the target nucleus are also used to constrain the isovector part of the optical potential. Lane consistent OMP is derived for all actinides if corresponding multiband coupling schemes are defined. For even-even (odd-A) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy-independent geometry. A phenomenological optical-model potential that couples multiple bands in odd-A actinides is published for a first time. Calculations using the derived OMP potential reproduce measured total cross-section differences between several actinide pairs within experimental uncertainty for incident neutron energies from 50 keV up to 150 MeV. The importance of extended coupling is studied. Multiband coupling is stronger in even-even targets owing to the collective nature of the coupling; the impact of extended coupling on predicted compound-nucleus formation cross section reaches 5% below 3 MeV of incident neutron energy. Excitation of multiple bands in odd-A targets is weaker owing to the single-particle nature of the coupling. Coupling of ground-state rotational band levels in odd-A nuclei is sufficient for a good description of the compound-nucleus formation cross sections as long as the coupling is saturated (a minimum of seven coupled levels are typically needed).

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“…In principle the calculations could be carried out with the full neutron and proton density distributions given by the HFB calculations, as has been done in numerous earlier calculations (see, for a recent example, ref. [10]). The current procedure is a useful simplification in the present context, since we are interested in the effects of the overall size of the neutron and proton distributions, rather than in fine details of the radial distributions.…”

Section: Implications For Neutron-induced Reactionsmentioning

confidence: 99%

Deviation of nuclear radii from a smooth A dependence for neutron data

Dietrich

Anderson

Bauer

et al. 2007

Nd2007

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Abstract. Experimental values for r.m.s. charge density radii show deviations from a simple A 1/3 dependence of several percent for statically deformed nuclei and around shell closures. These data, for both stable nuclei and nuclei away from the valley of stability, are well described by Hartree-Fock-Bogolyubov calculations carried out at Bruyères-le-Châtel. By using the neutron and proton r.m.s. radii from these same HFB calculations in conjunction with a folding model to produce an optical potential, we can then predict the expected results from neutron scattering experiments. We have made a detailed study of this procedure in the A = 40-70 mass range. The calculated 14-MeV neutron nonelastic and total cross sections show deviations of several percent from a smooth dependence on A. We conclude that using mean field -folding model calculations is useful for estimating neutron cross sections on nuclei both on and away from the valley of stability.

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Importance of isovector effects in reproducing neutron total cross section differences in the W isotopes

Cited by 26 publications

References 38 publications

Is a global coupled-channel dispersive optical model potential for actinides feasible?

Is a global coupled-channel dispersive optical model potential for actinides feasible?

Nucleon scattering on actinides using a dispersive optical model with extended couplings

Deviation of nuclear radii from a smooth A dependence for neutron data

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