We show that the profiles of the Ni K${\mathrm{\beta }}_{1,3}$,β’ x-ray fluorescence spectra of ${\mathrm{NiF}}_2$ and NiO, which were long believed to originate from the multiplet splittings due to an exchange interaction between the x-ray hole and valence unpaired electrons, are clearly interpreted by a charge-transfer effect during the photoionization of one of the 1s electrons. The profiles of the Kβ x-ray fluorescence spectra of ${\mathrm{NiCl}}_2$, ${\mathrm{NiBr}}_2$, and ${\mathrm{NiI}}_2$ are also predicted from the charge-transfer effect. The range of validity of the present theory and its relation to the shakeoff satellites are also discussed.

• Received 5 July 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.2193