Low-symmetry fields

The authors have interpreted their data using a statistical model, which reveals that the energy gap between the 1 Aj ground state and the lowest of the spin-orbitally split ST2 levels is temperature dependent the form of this temperature dependence changes with x. The model includes spin-orbit coupling, low-symmetry field distortion, covalency, and dynamic as well as static effects of local ligand vibrations. 

Here Sg and are the tetragonal and orthorhombic components of the low symmetry field, sometimes called strain terms. The signs of Sg, are chosen to conform with the signs for the two coordinates Qg and respectively. All parameters in Eqs. (1) and (2) can have units of energy if dimensionless units are used for Qg and [2,8]. 

In the discussion of terms in low symmetry fields it is useful to adopt a ket notation of the form... 

Actually, the above argument was used in the reverse order to determine the orientation of the histidine on the basis of ESR data before x-ray determinations were available. Nevertheless, even though subsequent x-ray studies did not invalidate the conclusions based on ESR data, there is some doubt in attibuting the low symmetry field to the position of the histidine (37). The magnitude of the effect does not appear to be sufficient. 

Next, it is necessary to estimate A Ex, A Ey and A Ez. It is recalled that Ti arises from the electronic configuration e. If the ta-orbitals are not degenerate, as would be the case in a low symmetry field, the three spatial components of Ti will have different energies corresponding to the different ways in which four electrons can distribute themselves among the three ta-orbitals. These arrangements are C and... 

Spin-free Fe(diimine)zX2 complexes show a weak broad band at 8.5—12.5 AK with two more or less clearly resolved components separated by ca. 2 AK. Kdnig et al. (33,34,40) associate this band with the 5X2 - transition, the excited E state being split by low symmetry field components. For spin-free l e(bipy)2(NCS)2 and Fe(phen)2(NCS)2, 10 Dj is estimated at 11.2 and 11.8AK, respectively. 

Do - Fi transitions implies a low symmetry field at the europium site (23). 

Because they can, and usually do, remove orbital degeneracies—and thus reduce the orbital contribution to the magnetism—low-symmetry ligand fields cannot be ignored in a study of the magnetic properties of transition metal complexes. Unfortunately, it is no easy matter to determine the splitting effects of low symmetry fields usually it is necessary to work with two... 

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