Lifetimes of the 91- and 531-keV States in Promethium-147

The lifetimes of the 91- and 531-keV states in ${\mathrm{Pm}}^{147}$, populated in the $\beta$ decay of ${\mathrm{Nd}}^{147}$, are determined employing a time-to-pulse-height converter arrangement similar to that of Green and Bell. The half-life of the 91-keV state, determined by the slope method, yielded a value 2.46±0.07 nsec. The mean-life of the 531-keV state, determined by the centroid-shift method, yielded a value (1.2±0.22)×${10}^{-10\mathrm{}}$ sec. These values are employed to determine the $M1\mathrm{}$ and $E2\mathrm{}$ transition probabilities, and are compared with the values obtained from the single-particle estimates and the values estimated by employing the Kisslinger-Sorensen-type wave functions and also those of Choudhury and O'Dwyer for the ground and the 91-keV states of ${\mathrm{Pm}}^{147}$. From the experimental transition probabilities the 531-keV state is inferred to contain sizable parts of the $\frac{7}{2}+$ phonon and the $\frac{5}{2}+$ phonon contributions.