MULTI-QUASI-PARTICLE AND ROTATIONAL STRUCTURES IN W-179 - FERMI ALIGNMENT, THE K-SELECTION RULE AND BLOCKING

High-spin states in W-179 have been studied following the (Er(C, 4n))-Er-170-C-13 reaction. Rotational bands up to I approximately 53/2hBAR have been identified, based on 1-, 3-, 5- and 7-quasiparticle structures. Different alignment mechanisms compete in the generation of angular momentum at the yrast line. A Fermi-aligned (i13/2)2 structure, coupled to high-K and to the 7/2-[5/4] orbital, forms the negative-parity yrast sequence above I(pi) = 31/2-. This may be called a ''t-band'' since its description within the cranking model requires a ''tilting'' of the cranking axis. The anomalous decay of the K(pi) = 35/2- 5-quasiparticle isomer is explained as arising from destructive interference of transition amplitudes coupling to the Fermi-aligned structure. Detailed analysis of the excitation energies of the multi-quasiparticle states indicates the quenching of both neutron and proton pair correlations, by comparison with blocking calculations.