Use of 24Na as a γ-ray calibration source above 3 MeV

We have reexamined the decay of 24Na to reduce the uncertainty in the intensity of the 3866-keV γ-ray and to demonstrate the use of the nuclide in extending energy and efficiency calibrations of high-resolution Ge detectors beyond 2754 keV. We find 3866.22(15) keV and 0.067(2)% for the energy and intensity, respectively, of the γ-ray deexciting the 5235.20(8)-keV level in 24Mg. For sources placed close to the detector, the 4122.66(2) sum peak is equivalent in statistical precision to a γ-ray of 5–10% intensity. The sum peak at 5234.9(2) keV is sufficiently well-resolved to confirm an energy calibration to ∼0.5 keV.