A XANES investigation of the bonding of divalent lead in solids

Abstract

XANES (X-ray absorption near-edge structure) spectra of divalent lead compounds have been studied at both the Pb L_III and L_I edges using synchrotron x rays from CHESS (Cornell High Energy Synchrotron Source). The combined L_III and L_I near-edge spectral features strongly support a sρ³d² hybridization scheme in covalently bonded yellow PbO. The absorption features associated with the spectra of ionic halides (PbF₂, PbCl₂, and Pb_I2) and the oxysalts [Pb(NO₃)₂, PbSO₄, and PbCrO₄] have been shown to be consistent with crystal field splittings of the final states using group theoretical arguments. The XANES spectra of a series of PbO-PbCl₂ glasses have also been studied to elucidate the nature of bonding and confirm the local structure derived from x-ray diffraction experiments. Shape resonance features associated with L_III and L_I edge XANES have also been discussed. This investigation illustrates the novel use of XANES spectroscopy in studying the bonding of nontransition metal ions.