Lifetimes of states in 150Nd were measured using the recoil distance method following Coulomb excitation of 150Nd by a 132 MeV 32S beam. The experiment was performed at the Yale Tandem accelerator, employing the SPEEDY gamma-ray detector array and the New Yale Plunger Device. Reduced transition probabilities in 150Nd are compared to the predictions of the critical point symmetry X(5) of the phase/shape transition that occurs for the N = 90 rare earth isotones. Very good agreement was observed between the parameter-free (apart from scale) X(5) predictions and the low-spin level scheme of 150Nd, revealing this as the best case thus far for the realization of the X(5) symmetry.
Collective E2 strengths were measured to probe the two-phonon ␥-vibrational character of I K ϭ4 4 ϩ states for 188,190 Os. Lifetimes for states with spin up to 8 ϩ of the ground-state band, 6 ϩ of the ␥ band, and the 4 ϩ state of the K ϭ4 ϩ band were measured by the recoil-distance method following Coulomb excitation by a 58 Ni projectile at E lab ϭ275 MeV. These lifetime data are compared with the electromagnetic matrix elements measured by previous Coulomb excitation experiments. The good agreement between these independent measurements supports the conclusion, made by the Coulomb excitation work, that the electromagnetic properties of these osmium nuclei are consistent with the description of ␥-soft collective models. In addition, it supports the evidence that the two-phonon ␥-vibration configuration is the dominant component for the lowest-lying I K ϭ4 4 ϩ states in osmium nuclei.
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