Russell-Saunders coupling metals

The first-order JT effect is important in complexes of transition metal cations that contain nonuniformly filled degenerate orbitals, if the mechanism is not quenched by spin-orbit (Russell-Saunders) coupling. Thus, the JT effect can be expected with octahedrally coordinated and high spin d cations, and tetrahedrally coordinated and d cations. The low-spin state is not observed in tetrahedral geometry because of the small crystal field splitting. Also, spin-orbit coupling is usually the dominant effect in T states so that the JT effect is not observed with tetrahedrally coordinated d, d , d, and d ions. 

This is known as Russell-Saunders coupling, and it will not be discussed any further because, for the most part, the orbital angular momentum of the transition-metal cations of the l>d series that are responsible for most of the magnetic properties exhibited by ceramic materials is totally quenched, that is, L = 0. Needless to say, this greatly simplifies the problem because now J = S and is given by... 

A further feature that separates first-row f d) transition metal complexes from those of the second- Ad) and third- 5d) row metals is that spin-orbit coupling is considerably smaller for the 3d metal series. For first-row complexes, therefore, the Russell-Saunders coupling approximation is reasonably valid. As a conse-... 

With light elements (e.g. first-row and second-row transition metals), to which principal consideration is given in this book, the Russell-Saunders (or IS) coupling scheme suffices. Every microstate is designated with a term symbol of the general form where 25 -I- 1 is the spin multiplicity (5 = 5,), L is the total orbital angular momentum... 

In 2d transition metal complexes, the splitting of the Russell-Saunders terms due to spin-orbit coupling is in general more important than the one caused by the external magnetic field typically used in EPR experiments. Therefore, the description of the... 

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