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

violating parts SV from the total Hamiltonian H <strong>of</strong> the TCSM. Then the diabatic states are the
eigenstates <strong>of</strong> the difference H d = H − SV , which is taken as the diabatic TCSM-Hamiltonian
in the case <strong>of</strong> equal nuclei (symmetric system). Since the symmetry <strong>of</strong> Hd is higher than
that <strong>of</strong> H, the irreducible representations <strong>of</strong> the Hd symmetry group appear to be, generally
speaking, reducible representations <strong>of</strong> the H symmetry group. Thus two different irreducible
representations <strong>of</strong> the Hd symmetry group can contain the same irreducible representations <strong>of</strong>
the H symmetry group. Therefore, in the general case the Hd eigenvalues possessing the same
symmetry relative to the H symmetry group may cross. This crossing will become an avoided
crossing if the perturbation SV , which is nondiagonal in the quantum numbers specifying the
Hd eigenvalues, is taken into account. For slightly asymmetric systems, the diabatic states are
defined by the expansion <strong>of</strong> the asymptotic states in terms <strong>of</strong> such maximum symmetry states.
Keeping the expansion coefficients fixed as functions <strong>of</strong> the collective coordinate q, diabatic
states are obtained with the desired property that their wave functions adjust to the shape <strong>of</strong>
the TCSM potential by a minimum change in their structure. Diabatic levels obtained with
this method agree with those from the maximum overlap procedure [57]. In the calculations we
use the method <strong>of</strong> maximum symmetry because it turns out to be numerically easier to handle.
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