Precision Measurement of theLX-Ray Spectra of Uranium and Plutonium

Twenty uranium $L$ x-ray transitions have been measured using a commercial, sealed off, uranium target x-ray tube. Twelve plutonium $L$ x-ray transitions have been measured in conventional x-ray fluorescence from a 5.86-g sample. All lines were measured with high precision using the two-crystal spectrometer, and corrected for the effects of temperature on the grating space of calcite, the effects of vertical divergence, and the effects of crystal diffraction pattern asymmetry. The wavelengths corresponding to these transitions are given in terms of the x-unit (where the latter is so defined that the wavelength of the Mo $K{\alpha }_1$ line is 707.8490 x-units) with relative errors of less than 15 ppm (parts per million) in the case of U, and less than 30 ppm in the case of Pu.