Decay ofPm143andPm144

Radioactive ${\mathrm{Pm}}^{143}$ and ${\mathrm{Pm}}^{144}$ were produced by the bombardment of ${\mathrm{Pr}}^{141}$ with $\alpha$ particles. Gamma rays at 475 kev, 610 kev, and 695 kev are found to be associated with the decay of ${\mathrm{Pm}}^{144}$ by $K$-capture to ${\mathrm{Nd}}^{144}$. A 740-kev gamma transition is associated with the decay of ${\mathrm{Pm}}^{143}$ by $K$-capture to ${\mathrm{Nd}}^{143}$. Levels of ${\mathrm{Nd}}^{144}$ are placed at 695 kev (2+), 1305 kev (4+), and 1780 kev (6+) above the ground level. Assignments of spins of levels and multipolarities of gamma-ray transitions are based on the results of measurements of conversion coefficients and gamma-gamma angular correlations. A value of (13±4)×${10}^{-11\mathrm{}}$ sec was found for the mean life of the 1305-kev level of ${\mathrm{Nd}}^{144}$. An upper limit of 3×${10}^{-11\mathrm{}}$ sec was found for the mean life of the 695-kev level of ${\mathrm{Nd}}^{144}$.