Octahedral fields

Mulliken symbols The designators, arising from group theory, of the electronic states of an ion in a crystal field. A and B are singly degenerate, E doubly degenerate, T triply degenerate states. Thus a D state of a free ion shows E and Tj states in an octahedral field. 

Figure 7.38 Splitting of d orbitals in a regular octahedral field...

The and 72 states are broadened as a result of slight variations in the crystal field. The 72 and E states are sharper but the E state is split into two components, 29 cm apart, because of the slight distortion of the octahedral field. Population inversion and... 

In tetrahedral fields the splitting of the free ion ground term is the reverse of that in octahedral fields so that, for d ions in tetrahedral fields A2g(F) lies lowest but three spin-allowed bands are still anticipated.In fact, the observed spectra usually consist of a broad, intense band in the visible region (responsible for the colour and often about 10 times as intense as in octahedral compounds) with a weaker one in the infrared. The only satisfactory interpretation is to assign these, respectively, as, wj = 7 i (P)-i A2(F) and ut = i(F)- A2(F) in which case U = ) should be... 

In a cubic field three spin-allowed transitions are expected because of the splitting of the free-ion, ground term and the presence of the term. In an octahedral field the splitting is the same as for the octahedral d ion and the same energy level diagram (p. 1029) can be used to interpret the spectra as was used for octahedral Cr Spectra of octahedral Ni usually do consist of three bands which are accordingly assigned as ... 

For d ions in tetrahedral fields the splitting of the free-ion ground term is the inverse of its splitting in an octahedral field, so that ig(F) lies lowest. In this ca.se three relatively intense bands are to be expected, arising from the transitions ... 

Figure 3-16. Octahedral field spin-triplet terms arising for d ...

Figure 5-1. High- and low-spin arrangements of d electrons in strong octahedral fields.

Figure 7-7. Splitting of d orbitals for elongated and compressed octahedral fields.

Relative ligand field stabilization energies for 3d ions. Thick lines octahedral field ... 

The effect of crystal field splitting is easily seen by studying the absorption spectrum of [Ti(H20)6]3+ because the Ti3+ ion has a single electron in the 3d orbitals. In the octahedral field produced by the six water molecules, the 3d orbitals are split in energy as shown in Figure 17.3. The only transition possible is promotion of the electron from an orbital in the t2g set to one in the eg set. This transition... 

Gaseous Ion spectroscopic state Components in an octahedral field Total degeneracy... 

FIGURE 18.1 The splitting patterns for ground-state D and /Terms in an octahedral field. 

For a specific dn electron configuration, there are usually several spectroscopic states that correspond to energies above the ground state term. However, they may not have the same multiplicity as the ground state. When the spectroscopic state for the free ion becomes split in an octahedral field, each ligand field component has the same multiplicity as the ground state (see Table 18.3). Transitions between spectroscopic states having different multiplicities are spin forbidden. Because the T2g and Eg spectroscopic... 

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