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We present an absolute energy measurement of the Kβ1,3 (KM2,3) emission spectrum of scandium (Z = 21) accurate to 2.1 parts per million (ppm). The previous experimental uncertainty was estimated as 105 ppm, or 0.47 eV, therefore we improve the accuracy of this measurement by a factor of 50 for use in any x-ray standards. There is a long-standing discrepancy between the most recent experimental and theoretical values. This work reports a Sc Kβ peak energy of 4460.845 eV with estimated standard error uncertainty of 0.0092 eV. The satellite component centroids, line-widths, and relative intensities are determined as a sum of five Voigt functions. The same analysis and experimental method shown here can be applied to advanced experiments in quantum electrodynamics, astrophysics and particle physics on soft x-ray spectra. This value has reconciled some of the previous discrepancy. However, the theoretical value is still discrepant from the new experimental measurement by 1.745 eV with a much tighter constraint on the experimental uncertainty. This strongly strengthens the need for new theoretical calculations and experimental measurements. [ABSTRACT FROM AUTHOR]

Two characterisations of the Cu Kβ1,3 spectrum are developed, which are robust and transferable to other experimental x-ray geometries. By observing and considering the significant contribution of radiative Auger emission to the Kβ profile, we obtain an improved and more robust characterisation. The contribution of the KM2,3M4,5 and KM2,3N1 radiative Auger satellites to the Kβ1,3 spectrum is measured to be 1.96%. The contribution of radiative Auger emission is often significant and should be included in defining characteristic x-ray spectra. This is a step in the renewed efforts to resolve inconsistencies in characteristic x-ray spectra between theory and common experimental geometries. The spectrum was measured using a rotating anode, monolithic Si channel-cut double-crystal monochromator and backgammon detector. The experimental setup provides insight into the portability of spectral characterisations of x-ray spectra. [ABSTRACT FROM AUTHOR]