Decay schemes of 109 d 127mTe and 9.4 h 127gTe

Abstract Gamma rays emitted in the decay of a secular equilibrium mixture of 109 d 127m Te and 9.4h 127g Te and in the decay of 127g Te alone have been investigated using high-resolution Ge(Li) detectors. In the decay of the equilibrium mixture, five new γ-rays have been observed with energies: 172.1, 375.0, 618.6, 628.6 and 651.0 keV. New β-transitions observed in the decay of 127g Te are to levels at 375.0 keV and 618.6 keV, and a new transition to a 628.6 keV level is observed in 127m Te decay. Comparative β- and γ-ray counting of equilibrium 127 Te sources with a low-background, proportional counter and Ge(Li) detectors, respectively, established absolute values for β-group intensities to levels of 127 I. The I.T. branching of 127m Te was found to be 97.6 %, and the β-group intensity from 127g Te to the 127 I ground state is 98.8 %. The log ft values of 8.7, 9.7 and 8.7 for allowed β-transitions to the levels at 619, 375 and 203 keV, respectively, disclose severe hindrances that reflect dissimilarities in parent and daughter state wave functions. Hindered first-forbidden β-transitions were also observed.