Configuration dependent pairing from band crossing frequencies

Abstract Data are presented on the crossing frequencies of odd-parity rotational bands in 161 Er. The crossing frequencies are shown to be correlated with the sign and magnitude of the quadrupole moments of the valence neutron orbits in odd- N rare earth nuclei. This can be understood in terms of configuration-dependent “blocking” of pairing-energy contributions requiring the inclusion of quadrupole terms in the pairing-correlation energy.