EVEN-PARITY BANDS OF 108, 110, 112Ru

High-spin, even-parity bands in neutron-rich 108, 110, 112Ru nuclei were reinvestigated and considerably expanded by measuring many-fold prompt γ-ray coincidence events following the spontaneous fission of 252Cf with Gammasphere. Our high statistics data allow us to detect weaker transitions and bands not previously published. Also, gamma branching ratios, which are important for theory, are carefully measured from all levels. In 110Ru, we find a doubling of levels for both ground and quasi-gamma bands above the 8+ levels. There are likely two-phonon quasi-gamma bands in 110, 112Ru, as well as a bandhead level in 108Ru. The odd–even spin energy band staggering observed in the quasi-gamma bands in 108, 110, 112Ru and the doubling of levels in 110Ru present a challenge to theory.