Low-Intensity Conversion Lines fromSm151andSn113

The electron spectrum of ${\mathrm{Sm}}^{151}$ has been measured with a lens spectrometer and its gamma-ray spectrum with a scintillation spectrometer. The $L$-conversion coefficient of the 21.7±0.3 kev de-excitation of the first excited state of ${\mathrm{Eu}}^{151}$ is 20±4, with $\left(\frac{{\alpha }_L}{{\alpha }_{M+N}}\right)=2.2\mathrm{}\pm 0.4$ and $\frac{{\alpha }_M}{{\alpha }_N}=2.2\mathrm{}\pm 0.2$ indicating $M1\mathrm{}$ multipolarity. The low intensity of the conversion electrons relative to the continuous beta spectrum of end point 75.9±0.6 kev implies the existence of a weak beta transition whose end point is 54.2±0.7 kev. The beta branching ratio, 54.2-kev beta transitions/75.9-kev beta transitions, is $\frac{1.7}{100}$. ${\mathrm{Log}}_{10}\mathrm{ft}$ values for the two beta decays are 7.6±0.2 for the 75.9-kev decay and 8.8±0.2 for the 54.2-kev decay. A partial analysis of the decay in terms of the Nilsson-Gottfried scheme has been made, but no definitive assignment for the 21.7-kev state appears to be possible. Measurements of the electron spectrum of ${\mathrm{Sn}}^{113}$ with the lens spectrometer reveal the existence of a weak conversion line corresponding to a transition of 253 kev. The intensity of this conversion line is (2.8±1.0)×${10}^{-3\mathrm{}}$ of the intensity of the conversion line from the 392-kev transition. This relative conversion electron intensity indicates that the 253-kev transition leads to the 392-kev state of ${\mathrm{In}}^{113}$, implying the existence of an excited state at 645 kev. The existing uncertainty in the relative gamma-ray intensities for the two transitions makes it impossible to assign spin and parity to the 645-kev state; the decay scheme presented is therefore incomplete.