The Eurogam-1 array has been used to study $\gamma$ 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 $\mathrm{}(10-16)\mathrm{}\hslash$ have been deduced to be 5.88 ± 0.08 e b (${}_{}{}^{152}{}_{}{}^{}\mathrm{Nd}$), 5.75 ± 0.10 e b (${}_{}{}^{154}{}_{}{}^{}\mathrm{Nd}$), and 5.33 ± 0.16 e b (${}_{}{}^{156}{}_{}{}^{}\mathrm{Nd}$).

• Received 6 June 1994

DOI:https://doi.org/10.1103/PhysRevLett.73.2540