We review recent, and some less recent, measurements of several emission spectra of copper. The results are discussed with special emphasis on elucidating the structure of the K α 1,2 and K β 1,3 diagram lines and their underlying transitions. These lines are found to contain ≈30 % contribution from 3 d spectator hole transitions. Other multielectronic transitions, the 2 p spectator hole (satellites) and 1 s spectator hole (hypersatellites) transitions were also measured. They are discussed paying special attention to the evolution of the lineshapes and intensities from the excitation threshold to saturation. Trends in the measured quantities depending on the spectator hole’s shell and subshell are also discussed.

A high-resolution pure Cu K h ␣ 1,2 hypersatellite spectrum was measured by photoexcitation using synchrotron radiation. A shift E(K h ␣ 2 )ϪE(K␣ 1 )ϭ281.4Ϯ0.3 eV from the diagram lines, a splitting E(K h ␣ 1 ) ϪE(K h ␣ 2 )ϭ23.6Ϯ0.4 eV, and an intensity ratio RϭI(K h ␣ 1 )/I(K h ␣ 2 )ϭ0.29Ϯ0.02 are found for the two lines of the spectrum. Full-spectrum fits based on ab initio Dirac-Fock calculations agree well with the measured spectrum, when QED corrections and Breit interaction are included. A slightly higher calculated R may indicate that the intermediate coupling is not fully accounted for. The intensity's evolution from threshold ͑measured to be at 18.351Ϯ0.015 keV) shows an unexpectedly long saturation range extending up to ϳ30 keV. The intensity evolution deviates from the Thomas model, which should be valid in the adiabatic, near-threshold regime. The implications of our results for the Z variation of the coupling, correlations, and atomic interactions across the 3d transition elements are discussed.

The first pure high-resolution photoexcited K(h)alpha(1,2) hypersatellite spectrum from a hollow Cu atom is measured. Its K(h)alpha(2)- Kalpha(1) shift and the K(h)alpha(1,2) lines' splitting, widths, and intensity ratio are accurately determined. Such spectra are uniquely suited to study relativistic correlation effects, transition from LS to intermediate coupling, and the Breit-Wigner interaction. The threshold energy and the spectrum's evolution with excitation energy are also measured. The roles of relativity and Breit interaction are explored by comparison with ab initio Dirac-Fock calculations.

Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the Kh alpha hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.

Hollow atoms in which the K shell is empty while the outer shells are populated allow studying a variety of important and unusual properties of atoms. The diagram x-ray emission lines of such atoms, the K h ␣ 1,2 hypersatellites ͑HSs͒, were measured for the 3d transition metals, Z = 23-30, with a high energy resolution using photoexcitation by monochromatized synchrotron radiation. Good agreement with ab initio relativistic multiconfigurational Dirac-Fock calculations was found. The measured HS intensity variation with the excitation energy yields accurate values for the excitation thresholds, excludes contributions from shake-up processes, and indicates domination near threshold of a nonshake process. The Z variation of the HS shifts from the diagram line K␣ 1,2 , the K h ␣ 1 − K h ␣ 2 splitting, and the K h ␣ 1 / K h ␣ 2 intensity ratio, derived from the measurements, are also discussed with a particular emphasis on the QED corrections and Breit interaction.