High-spin intrinsic and rotational states in the stable nucleus177Hf:Evidence for reaction-dependent spin population

Abstract

The stable nucleus ${}^{177}$Hf was studied with time-correlated particle-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ techniques following the reaction ${}^{176}\mathrm{Yb}{(}^{9}\mathrm{Be},\ensuremath{\alpha}{4n)}^{177}$Hf at a beam energy of 70 MeV. New high-spin states include extensions to three-quasiparticle bands based on the ${K}^{\ensuremath{\pi}}{=23/2}^{+}$ and ${25/2}^{\ensuremath{-}}$ configurations, together with a new band associated with the ${K}^{\ensuremath{\pi}}{=19/2}^{\ensuremath{-}}$, ${T}_{1/2}=56$ \ensuremath{\mu}s isomer. Moreover, the band based on the five-quasiparticle ${T}_{1/2}$=51 minute, ${K}^{\ensuremath{\pi}}{=37/2}^{\ensuremath{-}}$ state has been found, and a band assigned to a new ${K}^{\ensuremath{\pi}}{=39/2}^{+}$, five-quasiparticle state. Values of ${(g}_{K}\ensuremath{-}{g}_{R}{)/Q}_{0}$ agree well with the configuration assignments made to new and previously known bands. Comparison with multiquasiparticle calculations that incorporate a Lipkin-Nogami treatment of pairing correlations with blocking, suggests that all of the most favored three- and five-quasiparticle states have been observed. The dependence of the $\ensuremath{\gamma}$-ray intensities on the angular yields of the $\ensuremath{\alpha}$ particles suggests that the population arises from two entry distributions: one associated with complete fusion of the beam with the target, the other with incomplete fusion.