3d遷移金属のX線吸収スペクトルのプレエッジピークは電気四重極遷移か電気双極子遷移か？

3d 遷移金属K殻XANESスペクトルのプレエッジピークについて，元素，配位数，対称性，d電子数ごとに整理した．プレエッジピーク強度，電気双極子，四重極遷移成分の寄与を偏光スペクトル，群論および理論計算をもとに解説した．1s 電子の励起ではd 軌道へは対称性とは無関係に電気四重極遷移しか起こらないが，d-p混成軌道を形成すれば軌道中のp成分への電気双極子遷移はXANESスペクトル中に強いピークとして観察される．d 軌道へのp成分の混成程度は対称性に支配され，群論により説明可能である．偏光スペクトルはプレエッジピークの評価に極めて有効である．

The features of pre-edge peaks in K-edge XANES spectra of 3d transition metal compounds were classified by kinds of elements, the coordination numbers, the symmetry and the number of d-orbital occupied. The electric dipole and quadrupole contributions were reviewed based on polarized spectra, group theory, and theoretical calculations. The transition of a 1s electron to 3d orbital gives weak preedge peaks due to the electric quadrupole transition for any symmetries. An intense preedge peak is assigned to an electric dipole transition to p-character in the d-p hybridized orbital. The mixing of a metal 4p orbital with the 3d orbital strongly depends on the coordination symmetry, the degree of which is predictable with group theory. The polarized spectrum is effective for assignment of preedge peaks.

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