A new method for determining the valence of lanthanide compounds: Lγ4 emission spectroscopy

We have examined the potential of L γ 4 emission spectroscopy as a new method for valence determination. Sm L γ 4 emission spectra of a mixed valence compound, SmB 6 , as well as Sm standard references were recorded using a multicrystal, multidetector spectrometer at 298 K. The L γ 4 spectra exhibited a large chemical shift (∼4.5 eV) and substantial profile changes depending on the Sm oxidation state. Splitting of the Sm L γ 4 band was attributed to spin-dependent atomic multiplets, and valence-dependent edge-shifts of the Sm L I XANES spectra strongly suggest that the chemical shift of the L γ 4 emission is mainly due to the screening effects of the Sm L I core. The L γ 4 spectrum of SmB 6 was well reproduced by the averaged spectra of SmS and SmF 3 , indicating a SmB 6 valence of 2.65 ± 0.03. The advantages of the L γ 4 method, including simple data treatment and no need for an excitation energy scan, will encourage its use in several areas of materials science. We have examined the potential of L γ 4 emission spectroscopy as a new method for valence determination.