Signature-splitting systematics of the positive-parity bands in odd-N rare-earth nuclei

Experimental values of the signature-dependent splitting in energy for the N = 91-101 isotopes of erbium ytterbium, hafnium, tungsten, and osmium (Z = 68-76) are extracted for the lowest positive-parity quasineutron configurations. A correlation is established between this splitting and the relative energy of the Fermi level, λ, and that of the Ω = 1/2 component of the i13/2 neutron orbital. Whereas cranking calculations based on deformations appropriate to no quasiparticle excitation underpredict the observed signature splitting, the splitting can be reproduced for N = 95-99 isotopes, when the deformation effect of exciting a positive-parity quasineutron is included. (orig.)