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

λ during the lifetime t 0 <strong>of</strong> the dinuclear system. The competition between two possible fusion
channels was studied. The λ—channel describes the transition <strong>of</strong> two nuclei into the compound
nucleus with the elongation coordinate λ for a fixed mass asymmetry η during the fusion.
The second channel, named η—channel, describes the evolution <strong>of</strong> the dinuclear system to the
compound nucleus as a change <strong>of</strong> the mass asymmetry η by nucleon transfer from the light
nucleus to the heavy one.
The quasi-fission process <strong>of</strong> the dinuclear system was studied solving a transport master-
equation for the exchange <strong>of</strong> nucleons between the parts <strong>of</strong> the dinuclear system, which also
takes the decay <strong>of</strong> the dinuclear system in the elongation λ into account.
In this work, we have obtained the following results:
• The diabatic effects in the entrance phase <strong>of</strong> the reaction give rise to hindrances for the
growth <strong>of</strong> the neck and for the motion to smaller relative distances.
• The diabatic potentials as a function <strong>of</strong> the elongation λ are similar to the phenomeno-
logical double folding potentials used in the dinuclear system model <strong>of</strong> fusion.
• For the asymmetric dinuclear system, the diabatic hindrance for the motion to smaller
elongations λ is smaller than for the symmetric dinuclear system. Therefore, its evolution to
the compound nucleus in λ is more favored.
• The potentials as a function <strong>of</strong> the mass asymmetry η at the touching configuration <strong>of</strong>
the nuclei calculated within the TCSM are similar to the ones calculated using other methods.
• The isotopic dependence <strong>of</strong> the fusion barrier in η, calculated within the TCSM, agrees
with the isotopic behaviour <strong>of</strong> the experimental surplus <strong>of</strong> energy ∆B exp = B exp − BBass above
the Bass barrier BBass.The value <strong>of</strong> B exp is defined as the value <strong>of</strong> the bombarding energy for
a fusion probability 0.5.
• The adiabatic and diabatic microscopical mass parameters for the neck degree <strong>of</strong> freedom
ε are much larger than the one obtained in the hydrodynamical model with the Werner-Wheeler
approximation. By applying the microscopical mass parameters, we find a relatively stable neck
during the time <strong>of</strong> reaction.
• The dinuclear system is stable against a melting in λ and ε. The diabatic effects and the
microscopic mass parameters give a justification for the use <strong>of</strong> the dinuclear system in heavy
ion collisions at low energies.
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