Radiations from Cerium-141

The beta spectrum of ${\mathrm{Ce}}^{141}$ has been examined with an intermediate-image spectrometer adapted for coincidence measurements. The beta decay was found to be complex with two beta groups of maximal energies 574±3 kev and 432±2 kev. The data obtained indicated the presence of a single gamma ray, with an energy of 144.9±0.7 kev. Coincidence measurements inferred that the gamma ray was in coincidence with the lower-energy beta group. Gamma-ray spectra obtained with a scintillation spectrometer and a thin-lens spectrometer indicated that only one gamma ray is present in ${\mathrm{Ce}}^{141}$. Transitions ascribed to higher- and lower-energy beta groups are $\Delta I=-1\mathrm{}$, "yes" and $\Delta I=0\mathrm{}$, "yes," respectively. The gamma ray is probably magnetic dipole radiation. An $f_{\frac{7}{2}}$ state, with odd parity, is assigned to the ground state of ${\mathrm{Ce}}^{141}$; a $g_{\frac{7}{2}}$ state, with even parity, is assigned to the first excited state of ${\mathrm{Pr}}^{141}$.