Spin contribution to a magnetic moment

Spin-orbit coupling has to be included in a discussion of the magnetic properties of transition metal complexes whenever a spin-derived magnetic moment and an orbitally-derived magnetic moment coexist. Spin-orbit 

There is a simple method by which one may discover whether spin-orbit coupling mixes two d orbitals. For each d orbital, note the number of its nodal planes which also contain the z axis (i.e.those in which the z axis lies on a nodal plane). If two d orbitals differ by either one or zero in these numbers then the two orbitals may be mixed by spin-orbit coupling. Using this approach it follows that spin-orbit coupling mixes d orbitals as indicated below. Numbers in brackets indicate the number of nodal planes which, for that orbital, contain the z axis  

The origin of this pattern will become more evident from the detailed discussion that will be given Sections 11.4 and 11.5. 

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