DIFFERENCES BETWEEN L(3) AND L(2) X-RAY-ABSORPTION SPECTRA OF TRANSITION-METAL COMPOUNDS

The differences between L(3) and L(2) edges of 3d and 4d transition metal complexes and compounds in octahedral symmetry are discussed. The main origin of these differences are the multiplet effects due to the coupling of the 2p core wave function and the 3d and 4d valence wave functions. The 3d and 4d spin-orbit coupling is a second origin of difference. For 3d systems the multiplet effects dominate all other interactions and the L(3) and L(2) edge are completely mixed and reordered. For 4d systems the core hole spin-orbit coupling is large and the L(3) and L(2) are separated by about 100 eV with a ratio close to 2:1. The differences between the L(3) and L(2) edge originate from the weight transfer between the t(2g) and e(g) peaks due to the multiplet effect. This weight transfer is about 25% for the L(3) edge and about 5% for the L(2) edge, which implies that for a comparison to single-particle calculations the L(2) edge is preferable to use. Partly filled 4d systems are low-spin and the occupation of the t(2g) states implies a decrease of the first peak. This decrease is stronger for the L(2) edge, implying an increase in the L(3):L(2) ratio. For 4d(5) systems transitions to the t(2g) hole are only possible at the L(3) edge due to the combined effects of 4d spin-orbit coupling and the dd multiplet effects.