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

the approximate expressions (Eqs. (5.36) and (5.37)), are nearly equal in both cases.
Similar results as in the adiabatic two-center shell model are obtained. The mass parameters
M λλ and M εε depend weakly on the mass asymmetry η and on the deformations β <strong>of</strong> the nuclei
(β = β1 = β2 for 110 Pd+ 110 Pd) at the touching configuration. This result is presented in
Fig. 5-5. One can observe a minimum <strong>of</strong> M λλ as a function <strong>of</strong> β in the reaction 110 Pd+ 110 Pd
around the ground state deformation <strong>of</strong> 110 Pd (β ≈ 1.2). Since we regard the widths <strong>of</strong> single-
particles states, the mass parameters depend more smoothly on the mass asymmetry η than
the mean field cranking masses. In comparison to Ref. [84], where the hydrodynamical-type
treatment was used, the shell effects are here more transparent in the present consideration
because all peculiarities <strong>of</strong> the single particle spectra are taken into account. Let us consider
the fragmentation 86 Kr + 134 Ba (η =0.2) in the system 220 U where the number <strong>of</strong> neutrons
in the fragments is close to the magic numbers 50 and 82, respectively, and the single particle
have a smaller slope with respect to λ than in the neighbouring combinations. We find a
levels
contribution to Mλλ from M smaller diag
λλ and a local minimum in the dependence <strong>of</strong> M λλ on η
(Fig. 5-5). For η0.7.
Therefore, we cannot calculate M εε at the moment for such large mass asymmetries, where a
strong increase <strong>of</strong> M εε with η is expected in accordance with Ref. [84].
The mass parameter M εε increases about two times with decreasing ε from 1.0 to0.5 or
with increasing neck as shown in Fig. 5-6 and depends weakly on the mass number A. Inthe
reactions 110 Pd+ 110 Pd and 48 Ca+ 172 Hf, which lead to the same compound nucleus 220 U, the
difference between the corresponding values <strong>of</strong> M εε becomes larger for small values <strong>of</strong> ε. Such a
behaviour correlates with the fact that the diabatic contribution to the potential energy grows
faster with decreasing ε in symmetric configurations than in asymmetric ones [35].
For fixed ε =0.75, the mass M λλ grows with decreasing elongation λ on average as shown
in Fig. 5-6 and is 5 times larger than the reduced mass at λ ≈ 1.3. The dependence <strong>of</strong> M λλ
on λ has fluctuations around an average upwards trend which are more pronounced with an
increasing total mass number A <strong>of</strong> the system (Fig. 5-6) and at smaller temperatures (Fig. 5-7).
The average trend is connected with an increase <strong>of</strong> the average slope <strong>of</strong> the single particle levels
with decreasing λ or ε and with the enlarged number <strong>of</strong> crossings between the diabatic levels.
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