The precise isotopic mass-difference values of Smith and Wapstra have been used as a reference in the determination of the energy of the 6129-keV $\gamma$ of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. This transition is widely used as an energy standard in nuclear spectroscopy and in muonic x-ray studies. The value of the $\gamma$-ray energy was found to be 6129.170±0.043 keV. The quoted uncertainty is approximately one order of magnitude smaller than that of previous determinations. Data from the measurements also indicate that the new and highly precise mass values form a self-consistent set.

RADIOACTIVITY ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$; measured $E_{\gamma }$ referred to mass scale.

• Received 9 June 1975

DOI:https://doi.org/10.1103/PhysRevC.12.1003