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

Chapter 6
In most reactions studied in chapter 3 [35] the diabatic potential has a minimum in the neck
parameter ε around ε = 0.65—0.85. Due to the large inertia and friction coefficient in the neck
coordinate ε obtained in chapter 5 [43], the DNS configurations with fixed neck parameters have
a long lifetime in comparison to the reaction time. In contrast to the Ref. [42], where the fusion
probability through the fission-type valley with small ε was considered, fusion probabilities P CN
obtained for fixed large ε depend correctly on the initial value <strong>of</strong> η in the entrance channel [34].
As in Ref. [42], the adiabatic treatment <strong>of</strong> fusion in λ yields fusion probabilities which are
considerably overestimated in comparison to the experimental data although a fixed large neck
ε is considered. The reason <strong>of</strong> this overestimate is clearly seen in Fig. 6-1, where the adiabatic
potentials for different fragmentations leading to the same compound nucleus 246 Fm are shown
as a function <strong>of</strong> λ at ε = 0.75. In contrast to experiment the hindrance <strong>of</strong> fusion in these
potentials is practically absent (P CN ≈ 1) because there is no fusion barrier for the motion
to smaller elongations λ. The diabatic effects in the entrance phase <strong>of</strong> the collision studied in
chapter 3 strongly hinder the motion <strong>of</strong> the system to smaller elongations λ. The study <strong>of</strong> the
transition from the diabatic potential to the adiabatic one in the motion <strong>of</strong> the system in λ
during the lifetime <strong>of</strong> the dinuclear system allows us to conclude whether the fusion is possible
in the elongation coordinate.
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