Multiquasiparticle states in the neutron-rich nucleus174Tm

Abstract

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