Radiations from Cerium-141

Abstract

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\ifmmode\pm\else\textpm\fi{}3 kev and 432\ifmmode\pm\else\textpm\fi{}2 kev. The data obtained indicated the presence of a single gamma ray, with an energy of 144.9\ifmmode\pm\else\textpm\fi{}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 $\ensuremath{\Delta}I=\ensuremath{-}1$, "yes" and $\ensuremath{\Delta}I=0$, "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 ${\mathrm{Pr}}^{141}$.