Radiations from Cerium-141

The beta spectrum of Ce¹⁴¹ 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 Ce¹⁴¹. Transitions ascribed to higher- and lower-energy beta groups are ΔI=-1, "yes" and ΔI=0, "yes," respectively. The gamma ray is probably magnetic dipole radiation. An f7/2 state, with odd parity, is assigned to the ground state of Ce¹⁴¹; a g7/2 state, with even parity, is assigned to the first excited state of Pr¹⁴¹.