Determination of the Lifetime of the First-Excited State ofGd152

The lifetime of the 344-kev level of ${\mathrm{Gd}}^{152}$ was measured by coincidence measurements between the beta spectrum of ${\mathrm{Eu}}^{152}$ and the $K$ conversion line of the 344-kev transition, using a double lens coincidence spectrometer. The time delay between the outcoming coincident pulses was converted to pulse height. From the calibrated shift of the centroids, using the self-comparison method, a mean lifetime of $\tau =(7.6\mathrm{}\pm 1.3)\times {10}^{-11\mathrm{}}$ sec was obtained. The transition probability is 20 times the single-proton value. Thus, although the level is not "rotational," it has considerable collective character.