215 research outputs found
Trajectory analysis for fusion path in superheavy-mass region
We propose an effective method for the precise investigation of the
fusion-fission mechanism in the superheavy-mass region, using the
fluctuation-dissipation model. The trajectory calculation with friction is
performed in the nuclear deformation space using the Langevin equation. In the
reaction Ca+Pu, the trajectories are classified into the
fusion-fission process, the quasi-fission process and the deep quasi-fission
process. By analyzing the time evolution of each trajectory, the mechanism of
each process is clearly revealed, i.e., it is explained why a trajectory takes
a characteristic path in this model. We discuss, in particular, the condition
under which the fusion path is followed, which is crucial in the discussion of
the possibility of synthesizing superheavy elements.Comment: 25 pages, 12 figures, accepted for publication in Nuclear Physics
Fusion hindrance and roles of shell effects in superheavy mass region
We present the first attempt of systematically investigating the effects of
shell correction energy for a dynamical process, which includes fusion,
fusion-fission and quasi-fission processes. In the superheavy mass region, for
the fusion process, shell correction energy plays a very important role and
enhances the fusion probability when the colliding partner has a strong shell
structure. By analyzing the trajectory in three-dimensional coordinate space
with the Langevin equation, we reveal the mechanism of the enhancement of the
fusion probability caused by `cold fusion valleys'. The temperature dependence
of shell correction energy is considered.Comment: 31 pages, 23 figures, Accepted for publication in Nuclear Physics
Pre-scission neutron multiplicity associated with the dynamical process in superheavy mass region
The fusion-fission process accompanied by neutron emission is studied in the
superheavy-mass region on the basis of the fluctuation-dissipation model
combined with a statistical model. The calculation of the trajectory or the
shape evolution in the deformation space of the nucleus with neutron emission
is performed. Each process (quasi-fission, fusion-fission, and deep
quasi-fission processes) has a characteristic travelling time from the point of
contact of colliding nuclei to the scission point. These dynamical aspects of
the whole process are discussed in terms of the pre-scission neutron
multiplicity, which depends on the time spent on each process. We have
presented the details of the characteristics of our model calculation in the
reactions Ca+Pb and Ca+Pu, and shown how the
structure of the distribution of pre-scission neutron multiplicity depends on
the incident energy.Comment: 19 pages, 12 figures, Accepted for publication in J. Phys.
Influence of microscopic transport coefficients on the formation probabilities for super-heavy elements
The formation probability is shown to increase by a few orders of magnitude
if microscopic transport coefficients are used rather than those of the common
macroscopic pictures. Quantum effects in collective dynamics are taken into
account through the fluctuating force, as exhibited in diffusion coefficients
for a Gaussian process. In the range of temperatures considered here, they turn
out to be of lesser importance.Comment: 20 pages, 9 figures, replaced by revised version accepted for
publication in NP
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