Lithium K‐edge XANES spectra for lithium compounds

Abstract Lithium K‐edge x‐ray absorption near‐edge structure (XANES) spectra of Li metal, Li 2 S, Li 2 O, LiOH·H 2 O, Li 2 CO 3 , Li 3 PO 4 , Li 2 SO 4 ·H 2 O and LiNO 3 were studied by the total electron yield method. Peaks were observed at 59.9, 60.3 and 61.4 eV in the XANES spectra of Li 3 PO 4 , Li 2 SO 4 ·H 2 O and LiNO 3 , respectively. The peak of the each sample was assigned as the core exciton. In the XANES spectra of Li 2 O, Li 2 S, Li metal, LiOH·H 2 O and Li 2 CO 3 , there were shoulder structures at the same energy. To clarify the origin of each peak, the XANES spectra were examined with the discrete variational (DV)–Xα molecular orbital method. Comparing the measured spectra with the calculated wavefunction, the shoulder structures at 61.8 eV (Li 2 O) and 60.4 eV (Li 2 S) in the XANES spectra were assigned as the core excitons, which appeared as remarkable exciton peaks in the lithium halide spectra. The spectrum of each lithium compound could be classified according to the shape of the core exciton peak, namely either a sharp or a shoulder structure. The strength of the ionic bond determined which of these shapes a core exciton peak assumed. Copyright © 2002 John Wiley & Sons, Ltd.