Tanabe-Sugano diagram with

Tanabe-Sugano diagrams with representative values of C/B are given in Figures 12-15 for the lower lying terms of each of the cF configurations, n = 1-5. They can be used to deduce the principal features to be expected of the spectra of complexes of all the first transition metal ions in approximate octahedral or tetrahedral stereochemistry. 

Fig. 10 Contributions to L-edge spectral shape (a) Ligand field and electron configuration of low-spin Fe(III). (b) The two transitions with a ratio of 1 4 that would be obtained in the absence of spin-orbit coupling and electron repulsion, (c) The five states that arrive from the addition of e -e repulsion, (d) d6 Tanabe-Sugano diagram with the transitions indicated on the strong field (right) side, (e) Spectrum simulated with the effects of the metal p core hole (both spin-orbit and repulsion), (f) Adds 3d spin-orbit coupling, (g) Shows the o and 7t density of states distributed across the final state spectrum...

Fig. 6.1 Tanabe-Sugano diagram for high spin Fe " in either octahedral or tetrahedral coordination (Sherman, 985, with permission).

In order to treat fully the problem of interpretation of spectra, it is common to use diagrams provided by Tanabe and Sugano, which provide an alternative means of depicting the variation of term energies with field strength. Tanabe-Sugano diagrams... 

From these considerations it is clear that complexes in spin equilibrium do not exist at the crossover point between high-spin and low-spin configurations represented on a Tanabe-Sugano diagram. The two states are electronic isomers with geometric and electronic structures well separated on either side of the crossover point. The energy required to reach the crossover point represents at least part of the activation energy for the spin state interconversion. 

The energy level structure of partly filled d-orbitals can best be described by crystal field theory as expressed in Tanabe-Sugano diagrams. These account for absorption and luminescence spectra and allow the spectra to be correlated with crystal structure. 

With the sample spectra discussed in this section, it is clear that the Orgel diagrams and/or Tanabe-Sugano diagrams are useful in making qualitative analysis for the spectra. However, there are also cases where quantitative treatments are indispensable in order to make definitive assignments and interpretations. 

We compare our observed spectra with Tanabe-Sugano diagrams, such as Fig. 1 for octahedral d3 and tetrahedral d7 and Fig. 2 for octahedral d8 (and tetrahedral d2). The variable in this diagram is not an energy but the ratio A/B between the subshell energy difference A (called (Ei — E2) or 10 Dq by certain authors) and the Racah parameter of in-terelectronic repulsion B. Hence, a higher value of A/B does not necessarily mean a blue-shift of the absorption spectrum if B decreases, it may sometimes correspond to a red-shift. 

Since the Tanabe-Sugano diagrams for d5-systems are symmetric with respect to octahedral and tetrahedral complexes, one can strictly speaking only determine the numerical value A. However, the choice of examples in Table 3 clearly demonstrates that the manganese (II) aqua ion is Mn(H20)g++ and not Mn(HaO)4++. 

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