Intensities of Gamma Rays from the Calibration SourceCo56

Abstract

The intensities and energies of $\gamma$ rays from 77.3-day ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ are especially useful for calibration of Ge(Li) detectors in the range 0.8-3.5 MeV. We have reexamined the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ $\gamma$-ray spectrum using a Ge(Li)-NaI (Tl) coincidence-anticoincidence spectrometer. This study revealed five previously unreported $\gamma$ rays with energies of 896, 1140.2, 1336, 1443.2, and 1461.9 keV, all of which could be assigned to transitions from levels already established in the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ decay. Other weak $\gamma$ rays with energies of 2276.1, 2374.2, 2522.6, 3599.2, and 3612.5 keV have been confirmed and their intensities have been determined more accurately. A summary of the latest available data for the ${}_{}{}^{56}{}_{}{}^{}\mathrm{Co}$ decay is presented in the form of weighted averages for $\gamma$-ray energies and intensities and an improved decay scheme.