Precise comparison and measurement of gamma-ray energies with a Ge(Li) detector II. 400–1300 keV

Abstract

The energies of 60 γ rays from 24 nuclides in the region 400 to 1300 keV have been measured with Ge(Li) spectrometers. The purpose of this work is to provide an extensive set of energy standards in this region. Typical uncertainties in the γ-ray energies are 15 eV at 600 keV (or 25 ppm) and 24 eV at 1100 keV (or 22 ppm). Several γ-ray energy values were obtained by using precise cascade γ-ray energies to compute the crossover energies. Other energies were then obtained by measuring small (< 304 keV) energy differences. These differences generally have uncertainties of < 5 eV. In this manner, two independent γ-ray energy sets were developed up to 1.3 MeV; these sets are based on the γ-ray energies from (1) 198Au and 182Ta or 59Fe, and (2) 192Ir and 160Tb. From comparison of the energy values in these two sets, it has been determined that above 0.8 MeV the sets are inconsistent by 17 ± 4 eV; however, this discrepancy is reasonable considering the magnitude of the uncertainties in the γ-ray energies. A detailed discussion of the contributions to the errors in the γ-ray energies shows that the major contribution comes from the uncertainty in the reference energies available. This indicates that improvements in the accuracies of a factor of two or more could be obtained with more accurate reference energies.