Pseudo-dipolar contributions

Aeon is caused by contact interactions of unpaired f-electron spin density with the ligand, while Adip is due to the magnetic anisotropy of the molecule, where geometric factors are important. Normally the isotropic shift of the organolanthanide compounds is due mainly to the dipolar contribution (Adip) (or pseudo-contact contribution) as the contact contribution (Aeon) is very low because of the very contracted nature of the lanthanide f-orbitals. 

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