STUDIES OF HIGH-SPIN STATES IN RARE-EARTH NUCLEI USING THE ANGULAR-MOMENTUM PROJECTION METHOD .3. SIGNATURE SPLITTING IN ODD MASS NUCLEI

The problem of signature splitting in odd-mass rare-earth nuclei is investigated by using the angular-momentum projection method. According to the present theory, the inversion of signature dependence observed in odd-proton nuclei is due to the crossing between a single-proton band (h11/2) and a band consisting of a single-proton state (h9/2) coupled to a neutron broken pair. In odd-neutron nuclei, in contrast, crossing between a single-neutron band (i13/2) and a band consisting of a single-neutron state (i13/2) coupled to a proton broken pair occurs at much higher spins, because the proton broken pair (h11/2(2)) is less aligned compared to that of the neutron (i13/2(2)). This is the reason why two types of odd-mass nuclei show rather different characteristics (e.g. 165Lu and 165Yb). We point out that such a difference would not arise if it originated from the effect of gamma-deformation (static) or gamma-vibration (dynamical), because there would be no essential difference in the ways the gamma-degree of freedom affects the (last) odd proton and odd neutron. It is therefore important that a theory has to be tested on both types of nuclei for the sake of consistency. We compare our theory with experiments over a number of odd-mass nuclei. The results are quite satisfactory.