0 2 4 6 8 10 12 14 16 18 20 0 2 4 I Energy(M e V) 0 2 4 6 8 10 12 14 16 18 20 22  I FIG. 3. Calculated (lines) and experimental (solid circles connected by lines) energies of ground- state band (a) and first negative parity band (b). Experimental values are taken from [12]. The same equidistant structure with the frequency slightly growing with angular mo- mentum holds for the first negative parity band. Again, the calculation shows that mainly two eigenstates of ˆ H$_{0}$ are present in the wave function. Namely, [ | I − 1 2 I − 1 2 ( I − 1)) × Y$_{1}$ ] ( IM ) and [ | I +1 2 I +1 2 ( I + 1)) × Y$_{1}$ ] ( IM ) . The contribution of the later component while being small at I =0 is growing with angular momentum. The energy differences between the states in the negative parity band at low angular momentum are again determined mainly by the frequency of the quadrupole oscillations of the heavy fragment. The angular momentum dependence of the vibrational frequency ω$_{vib}$ = E$_{γ}$/ 2, defined as a half of the energy difference between the energies of two neighborhood levels of the ground state band and of the first excited negative parity band is illustrated in Fig.4. One can see the sharp decrease of the experimental values of E$_{γ}$ for the transition 10 + → 8 + in the ground state band and for the transition 13 − → 11 − in the negative parity band which can be a consequence of the backbending phenomena. The backbending in these bands can be probably related to a rotational alignment of the nucleonic orbitals as it is mentioned in [12]. The model considered above does not provide a mechanism which could be responsible for the experimentally observed behavior of the γ -transition energies. However, it is seen from 12