0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 B(E2,I->I-2)/ B (E2,2 $_{+}$->0+ ) I FIG. 6. Angular momentum dependence of the ration of the reduced transition probabilities B ( E 2 ,I → ( I − 2)) /B ( E 2 , 2 + → 0 $^{+}$) for the quadrupole transitions between the subsequent levels in the ground state band and the first negative parity band. in both bands are the same. Thus, the experimentally observed staggering of BE 1 /BE 2 ratios can be attributed to the staggering of the B ( E 1) values (see Fig. 7). Such a staggering behavior of B ( E 1) can be qualitatively explained with the use of equation (28). We can see that the reduced transition probability B(E1) for the tran- sition from state I of the ground state band to the state ( I -1) of the first excited neg- ative parity band consist of two contributions, since both dipole transitions are allowed (see Eqs.(11,14)) from the component [ | I 2 I $_{2}$( I )) × Y$_{0}$ ] ( IM ) to [ | I 2 I $_{2}$( I )) × Y$_{1}$ ] ( I − 1 ,M ) and from [ | I − 2 2 I − 2 2 ( I − 2)) × Y$_{2}$ ] ( IM ) to [ | I − 2 2 I − 2 2 ( I − 2)) × Y$_{1}$ ( I − 1 ,M $_{)}$. In the opposite case of tran- sition from the states of the negative parity band to the states of the positive parity be- longing to the ground state band, we have only one allowed transition, namely from the component [ | I 2 I $_{2}$( I )) × Y$_{1}$ ] ( I +1 ,M ) to the component [ | I 2 I $_{2}$( I )) × Y$_{0}$ ] ( I,M $_{)}$. The transition from [ | I +2 2 I +2 2 ( I + 2)) × Y$_{1}$ ] ( I +1 ,M ) to [ | I − 2 2 I − 2 2 ( I − 2)) × Y$_{2}$ ] ( I,M ) is forbidden because the dipole operator does not change a number of the quadrupole phonons. The B ( E 1) /B ( E 2) ratios as a functions of an initial angular momentum are presented in Fig.7. Calculated ratios for the odd initial angular momentum (i.e. for transitions from the states of the negative parity) lie systematically lower than the ratios for the even initial 15