(2000-2005) RESEARCH GRANT IN MESSINA
Analysis of the influence of the entrance channel effect and shell structure
on the fusion–fission reaction mechanism in collisions of massive nuclei.
The research has been developed in the framework of the
scientific programme "
Super-heavy nuclei production around Z=114".
The calculations, based on the Di-Nuclear System concept (DNS), show that
entrance channel effects are important to describe the
experimental data in the case of collisions of massive nuclei.
The fusion excitation functions calculated in this way were
used to estimate the survival probability of the formed
compound nucleus (CN) in the framework of
advanced statistical models for the de-excitation cascade.
Comparing our calculations to the experimental excitation
functions of evaporation residues measured for different
mass-asymmetry reactions it is possible to evidence
how the entrance channel strongly affects the evaporation residue production.
Some reactions that have been studied are:
20Ne+234U and
78Ge+176Yb
(both leading to
254No CN),
32S+182W,
48Ti+166Er and
60Ni+154Sm (leading to
214Th CN),
86Kr+130Xe,
40Ar+176Hf and
124Sn+92Zr (leading to
216Th),
16O+204Pb and
96Zr+124Sn
(leading to
220Th CN), and the reactions
48Ca+243Am,
48Ca+248Cm,
48Ca+249Cf leading respectively to
291115,
296116 and
297118 superheavy compound nuclei.
The dependencies of the partial capture cross-section, the partial fusion cross-section and
the fission probability of the excited intermediate nuclei along the de-excitation cascade of the
compound nucleus have been also studied.
It has been found that the competition between quasifission and fusion (at the DNS stage) starts
from low values of the initial orbital angular momentum. The contribution of quasifission
increases with
L, and it is larger for the reaction induced
by a heavier ion beam.
For further reading, see:
A. Lamberto et al., Journal Phys. Soc. Jpn. 74 (2005) 307
A. Lamberto et al., European Phys. Journal A 19 (2004) 89
A. Lamberto et al., European Phys. Journal A 22 (2004) 75
A. Lamberto et al., Journal Phys. Soc. Jpn. 72 (2003) 2509
A. Lamberto et al., Phys. Atom. Nucl. 66 (2003) 1071
