Effects of diabaticity on fusion of heavy nuclei in the dinuclear model ...

Chapter 8
8.1 Summary
Depending on the main degree <strong>of</strong> freedom used for the description <strong>of</strong> fusion, two different types
<strong>of</strong> models for fusion can be distinguished. The first type <strong>of</strong> models assumes a melting <strong>of</strong> nuclei
along the internuclear distance (or elongation λ) [15, 16]. The second type is the dinuclear
system model [17, 34]. Models describing the fusion process as an internuclear melting <strong>of</strong> nu-
clei <strong>of</strong>ten use adiabatic potential energy surfaces. These potentials are calculated with the
macroscopic-microscopic method <strong>of</strong> the Strutinsky formalism. Without regarding the competi-
tion between complete fusion and quasi-fission, the first type <strong>of</strong> models overestimates the fusion
cross section <strong>of</strong> heavy nuclei [18]. However, the dinuclear system model describes the experi-
mental fusion data quite well. In this model, the fusion process is considered as the evolution <strong>of</strong>
a dinuclear system caused by the transfer <strong>of</strong> nucleons from the light nucleus to the heavy one.
The dinuclear system consists <strong>of</strong> two touching nuclei, which conserve their individuality, and
evolves in the mass asymmetry η to a compound nucleus or decays in the elongation λ. The
model assumes that the motion <strong>of</strong> the dinuclear system to smaller elongations λ is strongly hin-
dered. This is phenomenologically described with a double folding potential in frozen density
approximation which shows a minimum near the touching configuration <strong>of</strong> the nuclei.
We have investigated the fusion and quasi-fission process <strong>of</strong> heavy nuclei using the two-center
shell model (TCSM). The diabatic potential energy surfaces as a function <strong>of</strong> the elongation λ,
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