Lifetimes in Neutron-Rich Nd Isotopes Measured by a Doppler Profile Method

Abstract

The Eurogam-1 array has been used to study $\ensuremath{\gamma}$ rays emitted following the spontaneous fission of a $^{248}\mathrm{Cm}$ source. Yrast level schemes for the neutron-rich nuclei $^{152,154,156}\mathrm{Nd}$ have been constructed. The stopping of the Nd fragments in the source material leads to Doppler-broadened line shapes for those states that have lifetimes comparable to the stopping time. This paper describes the first measurements of lifetimes of medium-spin states in very neutron-rich nuclei obtained from the analysis of these line shapes. The transition quadrupole moments for the yrast states in the spin range $(10\ensuremath{-}16)\ensuremath{\hbar}$ have been deduced to be 5.88 \ifmmode\pm\else\textpm\fi{} 0.08 e b ($^{152}\mathrm{Nd}$), 5.75 \ifmmode\pm\else\textpm\fi{} 0.10 e b ($^{154}\mathrm{Nd}$), and 5.33 \ifmmode\pm\else\textpm\fi{} 0.16 e b ($^{156}\mathrm{Nd}$).