Resonant photoemission in transition-metal chlorides

In the chlorides of Ni, Co, Fe, and Mn, the resonance between the excitations of valence electrons and the $3p$ electrons of the metal ions is observed over the whole parts of the valence-band spectra including ligand-derived bands as well as satellites. The trend of the systematic change in satellite---to---main-band separations in going from NiCl₂ to MnCl₂ is opposite to that in the energies of charge-transfer excitons, and this is discussed in connection with the electron-shakedown mechanism of the hole-induced covalency. Excitation spectra consist of two or three overlapping bands approximately with Fano line shapes. The q value characterizing a Fano line shape is larger for satellites and ligand-derived bands than for the $3d$ bands of the metal ions. The resonant enhancements of the ionization cross sections of the main bands increase from NiCl₂ to MnCl₂. These aspects are interpreted in terms of the hybridization of the $3d$ orbitals of the metal ions and the $3p$ orbitals of the ligand ion. The ordinary M2,3VV super-Coster-Kronig bands are very weak.