Core excitations above the $K$ edge result in $K\alpha$ characteristic x-ray emission. Understanding these spectra is crucial for high accuracies in investigations into QED, near-edge x-ray structure and advanced crystallography. We address unresolved quantitative discrepancies between experiment and theory for copper. These discrepancies arise from an incomplete treatment of electronic interactions. By finding solutions to relativistic multiconfigurational Dirac-Fock equations accounting for correlation and exchange corrections, we obtain an accurate reproduction of the peak energies, excellent agreement of theory with experiment for the line shapes, good convergence between gauges, and account for the $K\alpha$ doublet ratio of $0.522\pm 0.003:1$.

• Received 9 May 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.123002