Extreme ultraviolet photoemission of transition-metal chlorides excited with synchrotron radiation

Abstract

Synchrotron radiation monochromatized at energies 76, 61, and 40 eV has been used to obtain the photoemission spectra of valence electrons in Ni${\mathrm{Cl}}_2$, Co${\mathrm{Cl}}_2$, Fe${\mathrm{Cl}}_2$, and Mn${\mathrm{Cl}}_2$. Only slight dependence of the spectra on excitation energy is found for three excitation energies employed here. Although the observed gross features of the spectra are consistent with the x-ray photoelectron spectra of these materials, the profiles of the spectra are partly different from those of the x-ray photoelectron spectra. The contribution of the $3p$ electrons of ${\mathrm{Cl}}^{-}$ ions to the photoelectron spectra relative to those of the $3d$ electrons of transition-metal ions may be different between extreme ultraviolet and x-ray excitations. Detailed comparison with the x-ray photoelectron spectra has been made to separate the components arising from the $3d$ electrons of transition-metals ions. Their line shapes are in good agreement with the spectral distributions of the multiplet levels of the $3d$ electrons in the final states derived from a simple ligand-field treatment.