Influence of protons on backbending

Backbending in (at least the first half of) the rare earth nuclei seems to be determined by the alignment of an isub(13/2) neutron pair. This is supported by the disappearance of backbending due to the blocking of an isub(13/2) level by an odd neutron for example in 165Yb. Contrary to expectations backbending disappears also by adding an odd hsub(9/2) proton to sub(70)sup(166)Yb in sub(71)sup(167)Lu for this state (but is present if the odd proton is in the gsub(7/2) level). A theory is presented which explains the odd neutron and the odd proton nuclei. It turns out that the odd proton in 167Lu serves only as a type of catalyst for the alignment of an isub(13/2) neutron pair. The odd proton changes the deformation and moves the Fermi surface nearer (gsub(7/2)) or farther away (hsub(9/2)) from the nearest isub(13/2) neutron level. In one case one finds backbending and in the other case no backbending in 167Lu. (Auth.)