Electron-Capture Decay of Gadolinium-151

The photon and conversion electron spectra following electron-capture decay of ${\mathrm{Gd}}^{151}$ were studied. Transitions of 21.59 ($M1\mathrm{}$), 153.7, 175.0 ($M2\mathrm{}$), 243.8 ($E1\mathrm{}$), and 308.4 kev seen in these spectra and a very weak transition of 155±5 kev seen in coincidence with the 153.7-kev transition were assigned to the decay of ${\mathrm{Gd}}^{151}$. Relative photon, conversion-electron, and transition intensities were determined for some of the transitions, and coincidence measurements were made at resolving times of 4 and 40 microseconds. The 175.0-kev transition was observed to depopulate a metastable state with a half-life of 58±10 microseconds. A level scheme is proposed for ${\mathrm{Eu}}^{151}$ including the levels populated by Coulomb excitation, ${\beta }^{-}$ decay of ${\mathrm{Sm}}^{151}$, and electron-capture decay of ${\mathrm{Gd}}^{151}$.