Chemical Effects of Isomeric Transitions: Separation of the Isomers of Te127, Te129, and Te121

Abstract

The problem of the chemical separation of radioactive tellurium isomers has been reinvestigated. The separation efficiencies obtained with end‐window β‐particle detectors for Te¹²⁷ and Te¹²⁹ are significantly less than unity and are in agreement with the values determined by Williams. It is demonstrated, however, that these values are not proper in that they have not been corrected for differences in detection efficiencies for the different β particles which were observed. Use of γ‐ray spectrometry has overcome this difficulty; measurement of the relative rate of growth of an individual γ ray, from a sample in which the equilibrium between metastable‐ and ground‐state isomers has been disturbed by the chemical separation, determines the percent of isomer separation, independent of detection efficiency. The separation efficiencies for Te¹²⁷ and Te¹²¹ were found to 0.984±0.022 and 1.0±∼0.05, respectively. These results also were used in support of the concept that the chemical properties of the unstable Te species formed in internal conversion are essentially independent of the details of the nuclear decay, and are the same for all Te nuclides which decay via highly converted isomeric transitions. Application of these results to the study of the decay of Te¹²⁹ is then discussed. The apparent separation factors determined for the 0.475‐, 1.12‐, and 0.027‐MeV γ rays in Te¹²⁹ were, respectively, 0.952±0.007, 0.863±0.020, and 0.254±0.005. These values were used to obtain relative γ‐ray transition probabilities in Te¹²⁹ through an analysis of the dependence of the isomer separation process upon nuclear decay parameters.