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Consistent nuclear model for compound and precompound reactions with conservation of angular momentum. [14. 6 MeV]

Description: The exciton model is modified such that it automatically reduces to the usual evaporation formula after equilibrium has been reached. The result is further modified to conserve angular momentum in a form compatible with the Hauser-Feshbach formula. This approach allows a consistent description of intermediate excitations from which tertiary reaction cross sections can be calculated for transitions to discrete residual levels with known spins and parities. Level densities used for the compound c… more
Date: January 1, 1979
Creator: Fu, C.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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PRECO-D2: program for calculating preequilibrium and direct reaction double differential cross sections

Description: The code PRECO-D2 uses the exciton model for preequilibrium nuclear reactions to describe the emission of particles with mass numbers of 1 to 4 from an equilibrating composite nucleus. A distinction is made between open and closed configurations in this system and between the multi-step direct (MSD) and multi-step compound (MSC) components of the preequilibrium cross section. Additional MSD components are calculated semi-empirically to account for direct nucleon transfer reactions and direct kn… more
Date: February 1, 1985
Creator: Kalbach, C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Multiple preequilibrium decay processes

Description: Several treatments of multiple preequilibrium decay are reviewed with emphasis on the exciton and hybrid models. We show the expected behavior of this decay mode as a function of incident nucleon energy. The algorithms used in the hybrid model treatment are reviewed, and comparisons are made between predictions of the hybrid model and a broad range of experimental results. 24 refs., 20 figs.
Date: November 1, 1987
Creator: Blann, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Pairing interaction effects in exciton level densities

Description: Recent progress in pairing corrections for exciton state-density formulas used in pre-compound nuclear reaction theories is reviewed. These correction factors are, strictly speaking, dependent on the nuclear excitation energy U and the exciton number n. A simple formula for (U,n)-dependent pairing corrections has been derived, based on the BCS pairing equations for constant single-particle spacing, for the exciton state-density formula for one kind of Fermion. It has been shown that the constan… more
Date: January 1, 1989
Creator: Fu, C.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Application of multistep compound and multistep direct models for data evaluation

Description: We have implemented the quantum mechanical multistep compound (MSC) and multistep direct (MSD) theories of Feshbach, Kerman, and Koonin (FKK) for the calculation of nucleon-induced multistep reactions. Our code system, FKK-GNASH, uses the FKK theory for primary preequilibrium emission and describes subsequent equilibrium emission using the Hauser-Feshbach code GNASH. The MSC contribution yields emitted particles with angular distributions symmetric about ninety degrees, whereas the MSD contribu… more
Date: January 1, 1992
Creator: Chadwick, M.B. & Young, P.G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Comparison of 14 MeV isomer production of {sup 178m2}Hf and {sup 179m2}Hf using Feshbach-Kerman-Koonin and exciton preequilibrium models

Description: The {sup 178m2}Hf(16+) isomeric state has a 31-yr half life and could pose serious radioactive problems in nuclear fusion reactors if its production in 14 MeV neutron-induced reactions is significant. We present statistical/preequilibrium model calculations for the production of this isomer in the {sup 179}Hf(n, 2n) {sup 178m2}Hf reaction, as well as the 25-days 12.5{sup {minus}} isomer in the {sup 179}Hf(n,n{prime}){sup 179m2}Hf reaction, using two different preequilibrium models: the exciton … more
Date: November 1, 1993
Creator: Chadwick, M. B. & Young, P. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Excitations and Optical Properties of Phenylene Based Polymers

Description: A complex picture of phenylene-based polymers is developed which unifies features of band and molecular exciton models. It incorporates major experimental finding in direct, and photoinduced optical absorption, stimulated photoemission and photoconductivity. The authors give new assignments for the most disputed features and identify new ones as edge states. The authors confirm a low binding energy for the principle emitting exciton and show that it dominates also in the fundamental absorption.… more
Date: July 1, 1998
Creator: Kirova, N.; Brazovskii, S.; Bishop, A. R.; McBranch, D. & Klimov, V.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Electronic and optical response of functionalized Ru(II) complexes: joint theoretical and experimental study

Description: New photovoltaic and photocatalysis applications have been recently proposed based on the hybrid Ru(II)-bipyridine-complex/semiconductor quantum dot systems. In order to attach the Ru(II) complex to the surface of a semiconductor, a linking bridge -- a carboxyl group -- needs to be added to one or two of the 2,2'-bipyridine (bpy) ligands. Such changes in the ligand structure affect electronic and optical properties and, consequently, the charge transfer reactivity of Ru(II)-systems. In this stu… more
Date: January 1, 2008
Creator: Kilina, Svetlana; Tretiak, Sergei; Sykora, Milan; Albert, Victor; Badaeva, Ekaterina & Koposov, Alexey
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Partner: UNT Libraries Government Documents Department
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Use of Covariance Matrices in a Consistent (Multiscale) Data Assimilation for Improvement of Basic Nuclear Parameters in Nuclear Reactor Applications: From Meters to Femtometers

Description: A new approach is proposed, the consistent data assimilation, that allows to link the integral data experiment results to basic nuclear parameters employed by evaluators to generate ENDF/B point energy files in order to improve them. A practical example is provided where the sodium neutron propagation experiments, EURACOS and JANUS-8, are used to improve via modifications of 23Na nuclear parameters (like scattering radius, resonance parameters, Optical model parameters, Statistical Hauser-Feshb… more
Date: April 1, 2010
Creator: Palmiotti, G.; Salvatores, M.; Hiruta, H.; Herman, M.; Oblozinsky, P. & Pigni, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Consistent Data Assimilation of Structural Isotopes: 23Na and 56Fe

Description: A new approach is proposed, the consistent data assimilation, that allows to link the integral data experiment results to basic nuclear parameters employed by evaluators to generate ENDF/B point energy files in order to improve them. Practical examples are provided for the structural materials 23Na and 56Fe. The sodium neutron propagation experiments, EURACOS and JANUS-8, are used to improve via modifications of 23Na nuclear parameters (like scattering radius, resonance parameters, Optical mode… more
Date: September 1, 2010
Creator: Palmiotti, Giuseppe
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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