Program - Brookhaven National Laboratory

The optical model has a significant impact on many branches of nuclear reaction physics. The central
assumption of that model is that the complicated interaction between an incident particle and a nucleus can
be represented by a complex mean-field potential. An important feature of a good optical model potential is
that it can be used to reliably predict these observables for energies and nuclides for which no experimental
measurement data exist, while the ingredients of the model, either microscopic or phenomenological, are
physically well-behaved. From the view of the many-body theory the nucleon optical potential can be
identified with the mass operator of the one-particle Green function. The first and second order mass
operators of one particle Green function in nuclear matter are obtained, and the real and imaginary parts
of the optical potential for finite nuclei are obtained by applying a local density approximation. With certain
versions of the Skyrme interactions we have obtained the microscopic optical potential for finite nuclei which
shows that for certain energy regions the potential depth, shape, relative contributions of the surface and
volume parts, as well as the energy dependences are in reasonable agreement with the phenomenological
optical potentials and those based on realistic nucleon-nucleon interaction. The calculated results, such as
the total, nonelastic and differential cross sections and analyzing powers are in good agreement with the
experimental data and to certain extent comparable with the phenomenological optical potentials up to
100 MeV. The microscopic optical potentials for deuteron, helium-3 and alpha are obtained by the twoparticle,
the three-particle and four-particle Green function method through nuclear matter approximation
and local density approximation based on the effective Skyrme interaction. The radial dependence, the
volume integral per nucleon and the root mean square (rms) radii of the microscopic optical potential
are calculated. The reaction cross sections and elastic scattering angular distributions for nuclides in the
mass range 12≤ A ≤ 208 with incident deuteron, helium-3 and alpha energies from threshold up to 100
MeV per nucleon are calculated, and the calculated results are compared with the experimental data. The
calculated results of reaction cross sections and elastic scattering angular distributions are generally in
good agreement with the experimental data in most cases.
PR 103
Experimental Average Prompt Neutron Multiplicity as a Function of Total Kinetic Energy
of Fission Fragments Described by Point-by-Point Model Calculations
Iuliana Visan, Institute for Nuclear Research, POB 78, 115400-Mioveni, AG, Romania. Anabella Tudora,
University of Bucharest, Faculty of Physics, Bucharest-Magurele, POB MG-11, R-76900, Romania.
The Point by Point (PbP) model calculations of the average prompt neutron multiplicity as a function
of total kinetic energy (TKE) describe very well the experimental data of 252Cf (SF), 239Pu (nth,f)
and 235U(nth,f) over the entire TKE range, including not only the slope (dTKE/dν)-1 but also the flat
or decreasing behaviour at low TKE values. Present deterministic PbP model results of (TKE) are
analyzed comparatively with previous PbP (TKE) results based on the same multi-parametric matrix
ν (Z, A, TKE) and different manners of averaging this matrix over the fission fragment distributions, as well
as with previous and recent results of probabilistic Monte-Carlo treatments. The PbP treatment provides
average model parameters as a function of TKE that are used in the most probable fragmentation approach
giving (TKE) in very good agreement with experimental data, too. The most probable fragmentation
with average parameters depending on TKE has the advantage to predict (TKE) outside the TKE
range where experimental FF distributions exist and offers the possibility to provide results at many
TKE values in a very short calculation time compared to PbP and Monte-Carlo treatments. Possible
explanations of discrepancies between the slopes of different sets of experimental (TKE) data are
mentioned, too. Experimental fission fragment distributions Y (A, TKE) recently measured for 234U (n,
f) at more incident neutron energies covering the range from 0 2 MeV up to 5 MeV allow the PbP model
prediction of (TKE) for this fissioning system.
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