Abstract
Inconsistencies in accepted values (in x units) of x-ray reference lines have recently been demonstrated, although all are supposedly based on "good" calcite crystals. Factors supporting the selection of the W line as the X-Ray Wavelength Standard are critically discussed. A review is given of the experimental measurements which are used to establish the wavelength of this line on an absolute angstrom basis. Its value is W Å. This may be used to define a new unit, denoted by Å*, such that the W wavelength is exactly 0.2090100 Å*; hence 1Å*=1ű5 ppm. The wavelengths of the Ag , Mo , Cu , and the Cr have been established as secondary standards with probable error of approximately one part per million. Sixty-one additional x-ray lines have been used as reference values in a comprehensive review and reevaluation of more than 2700 emission and absorption wavelengths. The recommended wavelength values are listed in Å* units together with probable errors; corresponding energies are given in keV. A second table lists the wavelengths in numerical order, and likewise includes their energies in keV.
DOI:https://doi.org/10.1103/RevModPhys.39.78
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