Positron emission intensity in the decay of120gI

Abstract
The β+/EC ratio in the decay of120gI (T1/2= 1.35 h), i.e. the β+emission intensity, was measured for the first time using a high purity120gI source, which was produced by irradiation of 99.0% enriched120Te with 15 MeV protons, followed by a chemical separation of radioiodine. Both γ-ray and X-ray spectroscopy were applied. In the former case a comparison of the intensity of the annihilation radiation with that of the 1523 keV γ-ray of120gI was done and in the latter case with that of the Καor ΚβX-ray of the daughter tellurium. Corrections for very small contributions of121I and120mI impurities were evaluated. The literature values for the Iβ+of120gI range between 39 and 81%. Our measurements lead to a value of 56±3%.