The binding energies of ${}^{29}\mathrm{Si}$, ${}^{33}\mathrm{S}$, and ${}^{36}\mathrm{Cl}$ have been measured with a relative uncertainty of $<0.59\times {10}^{-6}$ using a flat-crystal spectrometer. The unique features of these measurements are (1) nearly perfect crystals whose lattice spacing is known in meters, (2) a highly precise angle scale that is derived from first principles, and (3) a γ-ray measurement facility that is coupled to a high-flux reactor with near-core source capability. The binding energy is obtained by measuring all γ-rays in a cascade scheme connecting the capture and ground states. The measurements require the extension of precision flat-crystal diffraction techniques to the 5- to 6-MeV energy region, a significant precision measurement challenge. The binding energies determined from these γ-ray measurements are consistent with recent highly accurate atomic-mass measurements within a relative uncertainty of $4.3\times {10}^{-7}$. The γ-ray measurement uncertainties are the dominant contributors to the uncertainty of this consistency test. The measured γ-ray energies are in agreement with earlier precision γ-ray measurements.

• Received 19 December 2005

DOI:https://doi.org/10.1103/PhysRevC.73.044303