Decay of 145Eu to levels in 145Sm

Abstract

The decay of 145Eu to levels in 145Sm was investigated. Singles γ-ray spectra were obtained with the use of Ge(Li) detectors, and β +- γ (NaI) and e-γ (NaI) coincidence measurements were performed. By intercomparison of the photon intensity data with published conversion-electron intensity data, K-shell internal-conversion coefficients were calculated for most of the transitions observed in the γ-ray spectra. From the β +- γ coincidence measurements, the 145Eu decay energy was found to be 2710±15 keV. A level scheme with 23 excited states in 145Sm was proposed based on results obtained from e-γ coincidence measurements, on transitions energies, intensities and multipole orders, on the measured decay energy and on data available from (d, p) reaction studies. Energies (in keV) and spin and parity assignments (enclosed in parentheses) for the proposed levels in 145Sm are as follows: 0( 7 2 −) , 894.1( 3 2 −) , 1423( 9 2 −) , 1437( 1 2 , 3 2 , 5 2 +) , 1548 3 2 +) , 1628( +), 1658( 3 2 , 5 2 −) , 1805( +), 1859( 1 2 , 3- 2 −) , 1877( 5 2 , 7 2 −) , 1972( 3 2 −) , 1997( 5 2 , 7 2 −) , 2111, 2134( 3 2 , 5 2 , 7 2 −) , 2156( 1 2 −) , 2193, 2276, 2293 ( ≦ 7 2 − ), 2329, 2346, 2388, 2427 ( ≦ 7 2 − ), 2482 and 2510. The (K-capture/ β +) ratio for the first-forbidden transition that populates the 894.1 keV state was measured to be 80(±50%) as compared to the theoretical ratio of 42 for an allowed transition. By the use of closed energy cycles and the measured 145Eu decay energy, the electron-capture decay energies for 153Ho and 149Tb are predicted to be 4.22±0.06 and 3.69±0.03 MeV, respectively.