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

are continuous with respect to z at z =0. Forz0, the oscillator frequencies ωz
must be determined numerically from the assumption <strong>of</strong> volume-conservation. With the method
suggested we can find the diabatic levels close to the adiabatic levels (Fig. 3-1). Differences
take place only near the crossing points. In contrast to Ref. [57], we can consider the diabatic
effects for any neck parameter ε. This yields a better shape parametrisation <strong>of</strong> the DNS.
3.2 Results and discussion
In the calculations, we firstly consider symmetric collisions <strong>of</strong> spherical nuclei and then analyse
asymmetric entrance channels, thermal and deformation effects. The diabatic contribution
∆V diab as a function <strong>of</strong> the elongation is presented for the reaction 100 Mo+ 100 Mo in Fig. 3-2.
The nuclei are considered as spherical with ε =0.74, which supplies realistic shapes <strong>of</strong> the
DNS for λ = 1.5 − 1.6. ∆V diab consists <strong>of</strong> contributions from neutrons and protons. The
diabatic contribution increases with decreasing λ or R because many diabatic levels cross the
Fermi level (Fig. 3-3). In general, the diabatic contribution increases with the mass number
A <strong>of</strong> the system because <strong>of</strong> the larger number <strong>of</strong> level crossings. The diabatic contribution
∆V diab <strong>of</strong> many symmetric systems selected along the line <strong>of</strong> beta stability shows diabatic shell-
structure effects [63, 64]. The role <strong>of</strong> these effects is demonstrated in Fig.3-4a by the diabatic
contributions <strong>of</strong> neutrons and protons for the systems 90 Zr+ 90 Zr and 96 Zr+ 96 Zr. While the
diabatic contributions <strong>of</strong> the protons are nearly the same in both the systems, the diabatic
contributions <strong>of</strong> the neutrons are quite different. As a result, the total diabatic potential is
more repulsive in the case <strong>of</strong> 90 Zr+ 90 Zr (Fig. 3-4b).
Further diabatic potentials are presented in Figs.3-4c and 3-5 for the systems 130 Xe+ 130 Xe,
136 Xe+ 136 Xe, 100 Mo+ 100 Mo and 110 Pd+ 110 Pd. The neck parameter is fixed at ε =0.74 and the
nuclei are considered as spherical. Excepting the potentials with the Xe isotopes (Fig. 3-4c),
the diabatic potentials for all these systems have a pocket near to the touching configuration
(λ =1.58) in which the DNS could stand some time and evolve in mass asymmetry. For smaller
elongations, the diabatic potential is strongly repulsive in all symmetric systems.
The diabatic potential is similar to the one calculated with the phenomenological double folding
potential. In Fig. 3-5 we compare the diabatic potential <strong>of</strong> the system 110 Pd+ 110 Pd with the
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