How accurately are energies and intensities measured by gamma spectroscopy

The accuracy of energy determination is limited by the accuracy with which the values for standards are known, which in the range of 60 - 700 keV amounts to (2.6 - 3)x10-6, in the range of up to 4.5 MeV to (4 - 6)x10-6 and for higher energies it is 20x10-6. Semiconductor and diffraction spectrometers are used for the measurements. The intensity of powerful gamma transitions is measured by leading metrological institutions using semiconductor spectrometers with an accuracy of 0.5 - 1%. (Ha)