Decay history and magnetic moments at high spin in 152Dy.

Abstract

Average magnetic moments as well as information on the time evolution of the continuum structure of $^{152}\mathrm{Dy}$ at high spin have been obtained using the transient hyperfine magnetic field acting on fast ions traversing a thin, magnetized gadolinium foil. $^{152}\mathrm{Dy}$ nuclei were populated by the $^{76}\mathrm{Ge}$${(}^{80}$Se,4n${)}^{152}$Dy fusion-evaporation reaction at E${(}^{80}$Se)=326.5 MeV. The target-ferromagnet arrangement corresponds to a time window of about 70t1100 fs, during which the excited nuclei experience the transient field interaction. The statistical \ensuremath{\gamma} rays, as well as the high-energy, ${\mathit{E}}_{\ensuremath{\gamma}}$>1200 keV, \ensuremath{\gamma} rays contributing to the collective E2 ``bump,'' exhibit a negligible precession, in accordance with the very short lifetimes of these states. The precession of the angular distribution of discrete yrast \ensuremath{\gamma} rays deexciting the nucleus from spin I\ensuremath{\sim}35\ensuremath{\Elzxh} down yields an average magnetic moment for states with 43\ensuremath{\Elzxh}\ensuremath{\ge}I\ensuremath{\ge}31\ensuremath{\Elzxh}. The resulting 〈g〉=0.21(2) is considerably lower than the collective value Z/A\ensuremath{\sim}0.43 and indicates an appreciable contribution from aligned neutrons to the lower-spin region populated within the above time frame. The results are discussed in the framework of model calculations of the \ensuremath{\gamma}-ray cascade.