ACCURATE MEASUREMENT OF MG AND AL K-ALPHA-1,2 X-RAY-ENERGY PROFILES

We have obtained new, accurate, high-resolution measurements of the en ergy distribution of Kalpha1,2 X-rays emitted in fluorescence from Mg and from Al. The energy profiles were obtained by measuring their Brag g diffraction with a double flat-crystal spectrometer equipped with ac curate angle encoders. Both potassium dihydrogen phosphate and ammoniu m dihydrogen phosphate crystals were used to check the index-of-refrac tion correction to Bragg diffraction, the largest source of uncertainl y in this measurement. Through the use of Cu Kalpha1 as a transfer sta ndard, these X-ray energies (or wavelengths) have been connected with the optical wavelength scale, and thus to the Rydberg constant R(infin ity). Separate Kalpha1 and Kalpha2 energies as well as the centroids a nd maxima of the Kalpha1,2 distributions are given for both Mg and Al: separate Kalpha1 and Kalpha2 energies for Mg are presented here for t he first time. Resulting uncertainty estimates are in the range 0.01 - 0.015eV.