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

to the ones obtained in adiabatic calculations because we took the width Γ k <strong>of</strong> single-particle
states into consideration. This is observed in Figs. 5-1and 5-6 comparing the values <strong>of</strong> M εε
at the touching configuration <strong>of</strong> the nuclei for the reaction 110 Pd+ 110 Pd. Due to the effect
<strong>of</strong> the width <strong>of</strong> the single-particle states, the occupation probabilities for single-particle levels
with zero widths are distributed over more levels. This effect partially destroys the difference
between the <strong>diabaticity</strong> and a<strong>diabaticity</strong> at crossings (or pseudo-crossings) <strong>of</strong> the single-particle
levels. We want to stress that the differences between the diabatic and adiabatic single-particle
levels appear only near the crossing points. Moreover, the distribution <strong>of</strong> the diabatic occupa-
tion numbers n(ɛ k) and the derivatives f k approaches the ones obtained in the adiabatic case
for fixed values <strong>of</strong> ε, λ and excitation energy <strong>of</strong> the system (Fig. 5-8). Since we showed the
similarity <strong>of</strong> the data obtained with adiabatic and diabatic levels using the same width, we can
use diabatic single particle states in further calculations <strong>of</strong> mass parameters in order to simplify
the numerical procedure.
The obtained mass parameter for the neck degree <strong>of</strong> freedom is 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.
In addition, a large energy threshold due to the diabatic (structural) forbiddenness effect [35, 36]
hinders the motion to smaller internuclear distances. Therefore, the DNS configuration exists
long enough, and thermal fluctuations in the mass asymmetry coordinate could develop and
lead to fusion and quasifission, which are the essential reactions in the DNS concept.
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