138 research outputs found
A study of the almost sequential mechanism of true ternary fission
We consider the collinear ternary fission which is a sequential ternary decay
with a very short time between the ruptures of two necks connecting the middle
cluster of the ternary nuclear system and outer fragments. In particular, we
consider the case where the Coulomb field of the first massive fragment
separated during the first step of the fission produces a lower pre-scission
barrier in the second step of the residual part of the ternary system. In this
case, we obtain a probability of about for the yield of massive
clusters such as \nuclide[70]{Ni}, \nuclide[80-82]{Ge}, \nuclide[86]{Se}, and
\nuclide[94]{Kr} in the ternary fission of \nuclide[252]{Cf}. These products
appear together with the clusters having mass numbers of --. The
results show that the yield of a heavy cluster such as \nuclide[68-70]{Ni}
would be followed by a product of -- with a large probability as
observed in the experimental data obtained with the FOBOS spectrometer at the
Joint Institute for Nuclear Research. The third product is not observed. The
landscape of the potential energy surface shows that the configuration of the
Ni + Ca + Sn decay channel is lower about 12 MeV than that of the Ca + Ni + Sn
channel. This leads to the fact, that the yield of Ni and Sn is large. The
analysis on the dependence of the velocity of the middle fragment on mass
numbers of the outer products leads to the conclusion that, in the collinear
tripartition channel of \nuclide[252]{Cf}, the middle cluster has a very small
velocity, which does not allow it to be found in experiments.Comment: 11 pages, 9 figure
Peculiarities of Nuclear Fusion in Synthesis of Superheavy Elements
The small probabilities of synthesis of new superheavy elements at GSI (Darmstadt, Germany), Joint Institute for Nuclear Research (Dubna, Russia), and RIKEN (Wako, Japan) during the last decade stimulate the experimental and theoretical studies of the nuclear reaction mechanism. 1– 4 In preparation of these experiments, the main aim is to reach maximum cross sections of the yield of evaporation residues (ER) as a result of the de-excitation of the heated compound nucleus which is formed in complete fusion of the projectile and target nuclei. Because the ER excitation function in the synthesis of superheavy elements has very narrow width for "cold fusion" reactions (5–10 MeV) with 208 Pb and 209 Bi targets 5 and the width of the "hot fusion" reactions with 48 Ca projectile on actinide ta
Effects of the entrance channel and fission barrier in synthesis of superheavy element =120
The fusion and evaporation residue cross sections for the
Ti+Cf and Cr+Cm reactions calculated by the
combined dinuclear system and advanced statistical models are compared. These
reactions are considered to be used to synthesize the heaviest superheavy
element. The Ti+Cf reaction is more mass asymmetric than
Cr+Cm and the fusion excitation function for the former reaction
is higher than the one for the latter reaction. The evaporation residue
excitation functions for the mass asymmetric reaction is higher in comparison
with the one of the Cr+Cm reaction. The use of the mass values
of superheavy nuclei calculated in the framework of the macroscopic-microscopic
model by the Warsaw group leads to smaller evaporation residue cross section
for both the reactions in comparison with the case of using the masses
calculated by Peter M\"oller {\it et al}. The Ti+Cf reaction is
more favorable in comparison with the Cr+Cm reaction: the
maximum values of the excitation function of the 3n-channel of the evaporation
residue formation for the Ti+Cf and Cr+Cm
reactions are about 0.1 and 0.07 pb, respectively, but the yield of the
4n-channel for the former reaction is lower (0.004 pb) in comparison with the
one (0.01 pb) for the latter reaction.Comment: 21 pages, 10 figures, 2 table
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