Decay ofPm148,Pm148m, andEu148

Abstract

The beta decay of ${\mathrm{Pm}}^{148}$ and ${\mathrm{Pm}}^{148m}$ (5.0 days and 45.5 days) and the electron capture of ${\mathrm{Eu}}^{148}$ (58 days) proceed to levels in ${\mathrm{Sm}}^{148}$. These activities have been investigated with scintillation and magnetic spectrometers, and coincidence and directional correlation techniques. ${\mathrm{Pm}}^{148}$ (5 day) decays via three beta branches to levels at 1460 kev, 551 kev, and the ground state, with the available energy being 2460±20 kev. The decay of ${\mathrm{Pm}}^{148}$ (45.5 day) and ${\mathrm{Eu}}^{148}$ each populate levels of 551, 1181, 1596, 1908, and 2098 kev in ${\mathrm{Sm}}^{148}$. The long-lived Pm populates additional levels at 2027 and 2197 kev, and ${\mathrm{Eu}}^{148}$ populates levels at 1886, 2148, 2201, 2697 (?), and 2780 kev. The experimental data are consistent with the 45-day state being approximately 140 kev above the 5-day state. Decay schemes consistent with the experimental data are presented.