Two-electron one-photon x-ray excitation measurements in cobalt

Simultaneous two-electron (K+L) one-photon excitations in cobalt were studied using X-ray absorption spectroscopy. The cross sections measured, 0.29% of that of the one (K) electron one-photon excitation, are in very good agreement with the authors' previous measurements on Ni. The two-electron excitation energies are about 30 eV higher than the sum of those required for exciting the electrons involved independently. The theoretical energy levels obtained by Delta SCF calculations are found to be higher than the measured ones by as much as 55 eV, and density functional theories of core-hole excitations.