Cu K-edge x-ray-absorption spectra for the chemically well-defined

{Cu}^{III}

-containing oxides,

{La}_{2}

{Li}_{0.5}

{Cu}_{0.5}

O_{4}

and

{LaCuO}_{3}

, have been carefully studied in order to correlate the complex spectral features with the copper valence, the local symmetry, and the bonding nature. According to the extended x-ray-absorption fine structure spectra, it was found that the (Cu-O) bond distances for both compounds agree well with the x-ray crystallographic data, but in x-ray absorption near-edge structure (XANES) spectra, a clear higher-energy shift of the Cu K-edge position was observed for both trivalent copper oxides compared to divalent ones of

{Nd}_{2}

{CuO}_{4}

and

{La}_{2}

{CuO}_{4}

. When the site symmetry of trivalent copper is lowered from

O_{h}

D_{4 h}

as in

{La}_{2}

{Li}_{0.5}

{Cu}_{0.5}

O_{4}

, the feature by the shakedown process was observed to be split to A and A’, corresponding to transitions to the ‖1

s^{1}

d^{n + 1}

L^{- 1}

p_{π}^{1}

〉 final state and ‖1

s^{1}

d^{n + 1}

L^{- 1}

p_{σ}^{1}

〉 one, respectively. Therefore, it is proposed that Cu K-edge XANES spectral fine features below the main edge should be interpreted with the molecular-orbital concept, mainly depending upon the copper valence and the crystal-field effect by the local symmetry on the copper site. This work also reveals that a spectral separation (∼2.7 eV) between

{Cu}^{II}

and

{Cu}^{III}

compounds is smaller than the theoretically expected one (∼4 eV), and the XANES spectrum of metallic compound shows a tendency of a lower energy shift compared to that of insulating or semiconducting one. Thus these facts should be taken into account when determining the presence of trivalent copper from Cu K-edge XANES spectra of copper-based superconductors.

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