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

higher collective velocities to replace the adiabatic basis states at pseudo-crossings by diabatic
states [54]. Diabatic states belong to crossing levels. This situation is illustrated in Fig. 2-1.
2-1: Diabatic and adiabatic levels at the Landau-Zener-Stückelberg (quasi-)crossing. In
Figure
diabatic motion the nucleon keeps the nodal structure (character) <strong>of</strong> the wave function.
the
Only for very small collective velocities, the nucleons are able to adjust their wave functions
adiabatically and follow the adiabatic levels. At higher collective velocities, a nucleon occupying
the lower level before the crossing with an unoccupied level will stay (while preserving the
character <strong>of</strong> its wave function) on the diabatic level and finds itself on the upper level after
the crossing. Quantitatively, this jump probability, which measures the degree <strong>of</strong> <strong>diabaticity</strong>,
is given by [53]
where
= exp(− J 1
), (2.1)
∆
| ∂(ɛ1 − ɛ2)/∂q |·| ∆=¯h ·
/2π | H q| ′
12 |2 . (2.2)
The quantity ∆ is proportional to the difference in the slopes <strong>of</strong> the diabatic levels and to
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