REINA() DE TRABALHO SOBRE FiSICA NUCLEAR NO BRASIL

38 Reg6es nuckares XX ,RTFNB
National Superconducting, Michigan State University, East
Lansing, MI, USA
H. R. SCHELIN
Centro Federal de Educaccio Tecnonol6gica, CEFET,
Curitiba, PR, Brazil
J. A. WINGER
Departament of Physics and Astronomy, Mississippi State
University, Mississipi State, USA
I . FINCK
Departament of Physics, Central Michigan University,
USA
H. LAURENT
Orsay, Prance
D. HIRATA
Institute of Physical and Chemical Research, REKEN
Woks, Sukarno, Japan
The reaction cross section at intermediate energies for
a variety of neutron rich isotopes with energies ranging
from 50 to 70 MeV/nucleon is calculated. The Glauber
and WKB approaches considered are described in
details in ref. [1]. The imaginary optical potential is
determined by knowing the profile function t(b), see
ref. [2]. The Pauli-blocking "in-medium" correction in
the optical potential were included. The real nuclear
optical potential is determined by the double folding
expression with no energy dependence. Both potentials,
real and imaginary, depend on the nucleon densities.
The densities are from the relativistic mean field
theory. Comparison with experimental data is done.
[1]M.S. Hussein, R.A. Rego and C.A. Bertulani, Phys.
Rep. Vol.201, N.5, ( 1991 ) 279.
[2]A. Vitturi and F. Zardi, Phys. Rev. C, Vol. 36, N.
4, (1987) .1404.
Spontaneous cold fission and cluster
radioactivity half lives calculation
S. B. DUARTE
Centro Btasileiro de Pesquisas Fisicas
M. GONcALVES
Institute de Radioprotecdo e Dosimetria
O. HOYOS, F. VELASQUEZ, F. GUZMAN
Institute Superior de Ciencias y Tecnologia Nuclear
In the last two decades cluster radioactivity and spontaneous
cold fission phenomena have called attention
both, from the experimental point of view [1,2], and
the theoretical framework[3,4,5]. These processes are
explained in terms of the models by including shell effects,
and the results obtained in this context are in
good agreement with the data.
After the observation of nuclear decay of 234 U in two
symmetric nuclei with total kinetic energy very near
of the available energy for the decay (Q-value), it has
been detected others cold fission processes ( 230Th[2],
24e,242pn[2,7], a4scm[1,8] and 252 016,91). Besides the
cluster radioactivity process, the cold fission phenomenon
has been considered as the newest source of information
about the fission path from the sadle point to
the scission. Theoretical approaches have tried to understand
the alpha decay, exotic cluster emission and
cold fission processes through an unifyed model[3].
In the present work we introduce half lives calculations
of a large range of nuclei in order to predict possible
new candidates to experirhental research. We applied
our previous unified model[4,5], discussing the use of
different inertial coeficients on the result of half lives
and yields of cold fission fragments_
[1]A. Benoufella et al., Nucl. Phys. A565 (1993) 563.
[2]M. Asghar et al., Nucl. Phys. A560 (1993) 677.
[3] E. Stefanescu, W. Scheid, A. Sandulescu and W.
Greiner, Phys. Rev. C53 (1996) 3014.
[4]S.B. Duarte and M. Gonsalves, Phys. Rev. C53
(1996) 2309.
[5]M. Goncalves and S.B. Duarte, Phys. Rev C48
(1993) 2409.
[6]H. H. Knitter, F. J.. Harnbsch and B. Jorgensen,
Nucl. Phys. A536 (1992) 221.
[7]M.A.C. Hotchis et. al, Nucl. Phys. A530 (1991)
111.
[8]G.M. Ter Akopian et. al, Phys. Rev. Lett. 73
(1994) 1477.
[9) Y.X. Dardenne et. al, Phys. Rev. C54 (1996) 206.
Kaon multiplicity calculation near threshold in
photonuclear reactions
S. DE PINA
Universidade Federal du Paraiba
E. C. OLIVEIRA, E. L. MEDEIROS, S. B. DUARTE
Centro Brasileiro de Pesguisas Fisicas
M. GONcALVES
Institute de Radiopmtecao e Dosimetria
Pious and kaons have been intensively studied in the
last two decades in the relativistic heavy ions reactions
context[1,2]. A renewed interest in the photoproduclion
of particles has appeared in order to explore: the
in-medium photon-nucleon interaction by using intermediate
energy (0.5-2.0 GeV) monochromatic beams.
It is observed that photonuclear reaction yields have
been currently interpreted in the framework of a twostep
interaction model. A rapid intranuclear cascade
phase develops from binary intranuclear collisions, reabsorption
of photoproduced pions, and scattering of
recoil nucleons. During the second reaction stage the
excited residual nucleus cools down by a mechanism
of competition between fission and particle evaporation
processes [?, 3]
Recently, we proposed a many body cascade calculation
for the rapid phase which takes into account the
dynamical evolution of the multiparticle collisional processes[4].
Results of this model showed that the pion