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Title: QUANTUM PRE-EQUILIBRIUM MULTISTEP DIRECT CALCULATIONS FOR NUCLEON SCATTERING ON SPHERICAL AND DEFORMED NUCLEI: A MICROSCOPIC APPROACH

Authors:
 [1];  [1];  [1];  [2];  [2];  [2]
  1. Los Alamos National Laboratory
  2. NON LANL
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1329832
Report Number(s):
LA-UR-07-2757
DOE Contract Number:
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: ND2007 - INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY ; 200704 ; NICE
Country of Publication:
United States
Language:
English

Citation Formats

DUPUIS, MARC, BONNEAU, LUDOVIC, KAWANO, TOSHIHIKO, BAUGE, ERIC, DELAROCHE, JEAN-PAUL, and GOGNY, DANIEL. QUANTUM PRE-EQUILIBRIUM MULTISTEP DIRECT CALCULATIONS FOR NUCLEON SCATTERING ON SPHERICAL AND DEFORMED NUCLEI: A MICROSCOPIC APPROACH. United States: N. p., 2007. Web.
DUPUIS, MARC, BONNEAU, LUDOVIC, KAWANO, TOSHIHIKO, BAUGE, ERIC, DELAROCHE, JEAN-PAUL, & GOGNY, DANIEL. QUANTUM PRE-EQUILIBRIUM MULTISTEP DIRECT CALCULATIONS FOR NUCLEON SCATTERING ON SPHERICAL AND DEFORMED NUCLEI: A MICROSCOPIC APPROACH. United States.
DUPUIS, MARC, BONNEAU, LUDOVIC, KAWANO, TOSHIHIKO, BAUGE, ERIC, DELAROCHE, JEAN-PAUL, and GOGNY, DANIEL. Tue . "QUANTUM PRE-EQUILIBRIUM MULTISTEP DIRECT CALCULATIONS FOR NUCLEON SCATTERING ON SPHERICAL AND DEFORMED NUCLEI: A MICROSCOPIC APPROACH". United States. doi:. https://www.osti.gov/servlets/purl/1329832.
@article{osti_1329832,
title = {QUANTUM PRE-EQUILIBRIUM MULTISTEP DIRECT CALCULATIONS FOR NUCLEON SCATTERING ON SPHERICAL AND DEFORMED NUCLEI: A MICROSCOPIC APPROACH},
author = {DUPUIS, MARC and BONNEAU, LUDOVIC and KAWANO, TOSHIHIKO and BAUGE, ERIC and DELAROCHE, JEAN-PAUL and GOGNY, DANIEL},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Apr 24 00:00:00 EDT 2007},
month = {Tue Apr 24 00:00:00 EDT 2007}
}

Conference:
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  • An introduction of the different quantum mechanics models is given for the calculation of pre-equilibrium multistep direct process for nucleon induced reaction. A practical application is presented for {sup 238}U neutron induced reaction at medium energy (10-20 MeV). The double differential cross-sections are calculated with no adjustable parameter and reproduced the data very well. The cross-sections are expressed as a sum of DWBA transition amplitudes computed with a microscopic two-body interaction. The exited states of the target are expressed as particle-hole excitations built from single particle states obtained with the HF+BCS calculation with a Skyrme force. We also perform amore » sensitivity study our calculations with respect to the ingredients of the model, namely the two-body interaction which generates the transitions and the target states description.« less
  • The authors present two principal advances in multistep direct theory: (1) A two-component formulation of multistep direct reactions, where neutron and proton excitations are explicitly accounted for in the evolution of the reaction, for all orders of scattering. While this may at first seem to be a formidable task, especially for multistep processes where the many possible reaction pathways becomes large in a two-component formalism, the authors show that this is not so -- a rather simple generalization of the FKK convolution expression 1 automatically generates these pathways. Such considerations are particularly relevant when simultaneously analyzing both neutron and protonmore » emission spectra, which is always important since these processes represent competing decay channels. (2) A new, and fully microscopic, method for calculating MSD cross sections which does not make use of particle-hole state densities but instead directly calculates cross sections for all possible particle-hole excitations (again including an exact book-keeping of the neutron/proton type of the particle and hole at all stages of the reaction) determined from a simple non-interacting shell model. This is in contrast to all previous numerical approaches which sample only a small number of such states to estimate the DWBA strength, and utilize simple analytical formulae for the partial state density, based on the equidistant spacing model. The new approach has been applied, along with theories for multistep compound, compound, and collective reactions, to analyze experimental emission spectra for a range of targets and energies. The authors show that the theory correctly accounts for double-differential nucleon spectra.« less
  • Microscopic optical model potentials are tested against a large body of measurements of elastic differential cross sections and analyzing powers for neutrons (8--40 MeV) and protons (16--60 MeV) scattered from targets ranging from {sup 6}Li to {sup 208}Pb. Reasonably good fits to the data can be found using only three parameters, {lambda}{sub V}, {lambda}{sub W} and {lambda}{sub SO}, normalizing constants to the real, imaginary and spin orbit potential, respectively. These parameters have a smooth dependence on energy and mass number. 17 refs., 8 figs.
  • We have recently developed an extension of the direct-semidirect (DSD) radiative capture model to unstable final states and have confirmed its utility in explaining the spectrum of rays from capture of polarized 19.6-MeV protons on {sup 89}Y. It was found that the extended DSD model, supplemented by a Hauser-Feshbach contribution, successfully explains the observed spectra, angular distributions, and analyzing powers, without requiring additional mechanisms, such as precompound or multistep emission, or nucleon-nucleon bremsstrahlung. In this contribution we show that the model also successfully explains data at higher energies (34 MeV incident protons), and that there is no need for additionalmore » contributions other than Hauser-Feshbach at this energy as well. The extended DSD model treats capture to unbound final states and also to bound single-particle states that damp into a compound system. An optical (complex) potential is used to describe the propagation of the captured particle. Application of this model to the {gamma} spectrum in the {sup 89}Y(p,{gamma} ) reaction at 19.6 MeV is shown. We have performed new calculations at higher energy (34 MeV protons), and have compared them with the spectra and angular distributions measured in [2] on targets of natural Cu, Ag, and Au. An example of the results, for the spectrum from Cu, is shown in the right-hand part of the figure. In both cases the DSD calculation is shown by a solid line, and a Hauser-Feshbach calculation by a dashed line. The 34-MeV calculations were very similar to those at 19.6 MeV as described in [1]. In both cases, the sum of DSD and Hauser-Feshbach calculations adequately describes the measured spectra. Although not shown, the angular distributions are also well described. There are no significant deficiencies in the comparison with experiment that indicate a need for multistep processes or other additional reaction mechanisms. Such processes are therefore required, if at all, only at significantly higher energies than reported here. On the basis of these results, we believe that the extended DSD model is the most appropriate tool for modeling the high-energy portion of the gamma spectrum from nu- cleon capture. On the other hand, simple precompound treatments such as the exciton model should remain important for emission in reactions with complex projectiles (e.g. d, {alpha}, heavy ions), as long as an easily-implemented quantum mechanical model is not available.« less