DIFFRACTION ANGLE MEASUREMENTS BEARING ON THE DEUTERIUM BINDING ENERGY AND ON THE X-UNIT-TO-MILLIANGSTROM CONVERSION CONSTANT

Abstract

Precise angle measurements of the deuterium de-excitation and annihilation radiations have been made with a double flat crystal diffraction spectrometer. The deuterium γ-ray was diffracted from the (211), (211); (211), (633); (211), (844); and (844), (844) planes of two calcite crystals. The energy comparison, based on angle measurements of the deuterium γ-ray diffracted from the (844), (844) and the annihilation γ-ray from the (211), (211) planes of the two crystals, is particularly insensitive to systematic geometric error. If the energy and standard error of the annihilation radiation is taken to be 510.978 ± 0.007 kev, the deuterium binding energy is 2224.52 ± 0.20 kev. Absolute angles were measured for both diffracted γ-rays. A knowledge of the absolute diffraction angle and the absolute wavelength of the annihilation γ-ray determines the absolute spacing of the diffraction plane of calcite, d₂₁₁ = 3035.70 ± 0.15 mÅ at 18 °C. With reference to the standard d₂₁₁ spacing of calcite, 3029.494 X-units, the conversion constant from X-unit to mÅ is 1.002049 ± 0.000057. The presently accepted value for the absolute wavelength of the annihilation radiation and the precise meaning of the term X-unit is more completely specified in the text.