High-K isomers and rotational structures in ¹⁷⁴W

High-spin states in ¹⁷⁴W (Z = 74) have been populated using the reaction ¹²⁸Te(⁵⁰Ti, 4n)¹⁷⁴W at beam energies of 215 and 225 MeV. The Gammasphere array was used to detect the γ rays emitted by the evaporation residues. Four previously known collective band structures have been extended, and 16 new rotational sequences observed. Two are built upon isomeric states, one corresponding to a two-quasiparticle K = 8 isomer, the other to a four-quasiparticle K = 12 isomer, with the latter exhibiting strong K-violating ΔK=12 decays to the ground state band. Nucleonic configurations for the two- and four-quasiparticle excitations are proposed, and Woods-Saxon cranking calculations are presented to understand the rotational structures. Decay mechanisms of multi-quasiparticle K isomers are discussed in terms of the prevalent phenomenological models, with special emphasis on γ-tunneling calculations. Surprisingly, the latter underpredict the decay hindrance for the K = 12 isomer by three orders of magnitude, unlike all other isomer decays in this mass region.