Multiquasiparticle states in the neutron-rich nucleus 174Tm

Deep inelastic and transfer reactions with an 820-MeV, 136Xe beam and various ytterbium and lutetium targets have been employed to study high-spin structures in the neutron-rich thulium isotopes beyond 171Tm. Results in the doubly odd nucleus, 174Tm, include the identification of numerous new two- and four-quasiparticle intrinsic states including several isomers below 1 MeV, and the observation of the Kπ=4^- ground state rotational band populated via direct decay from a τ=153(10)-μs, Kπ=14^- isomer at 2092 keV. The 398-keV, M1 transition linking the isomer and ground state band is abnormally fast for a highly forbidden, ΔK=10 decay. This relative enhancement is explained in terms of mixing of the 13^- level with the nearby 13^- member of a Kπ=8^- rotational band, with an interaction strength of V ≈ 1.4 keV. Multiquasiparticle calculations are compared with the observed states.