A Mass Spectrometric Investigation of Branching in Cu64, Br80, Br82 and I128

Abstract

An investigation of branching in certain neutron induced activities has been carried out by a mass spectrometric technique. Gram quantities of the elements in question were subjected to prolonged irradiation in a graphite moderated pile and were allowed to cool. The occurrence of negatron emission in the induced activities was identified with the presence in the irradiated sample of decay products of atomic number $Z+1\mathrm{}$; positron emission and orbital electron capture, with the presence of decay products of atomic number $Z-1\mathrm{}$. The amounts of these decay products were determined by adding to a solution of the irradiated sample, as tracers, weighed milligram amounts of the daughter elements in a form isotopically different from the radiogenic material. When isotopic mixing had occurred, the daughter elements were isolated for mass spectrometric analysis. In such a procedure, quantitative recovery is unnecessary: the branching ratio can be determined from the change in the isotopic constitution of the tracers. The following values of the branching ratio ${\lambda }_{\pm }$ (defined as the ratio of $Z\to Z-1\mathrm{}$ transitions to $Z\to Z+1\mathrm{}$ transitions) were determined: