Electronic spectra and magnetic moments actinoids

The spectroscopic and magnetic properties of actinoids are complicated and we mention them only briefly. Absorptions due to 5/-5/ transitions are weak, but they are somewhat broader and more intense (and considerably more dependent on the ligands present) than those due to 4f-4f transitions. The interpretation of electronic spectra is made difficult by the large spin-orbit coupling constants (about twice those of the lanthanoids) as a result of which the RusseU-Saunders coupling scheme partially breaks down. 

Magnetic properties show an overall similarity to those of the lanthanoids in the variation of magnetic moment with the number of unpaired electrons, but values for isoelec-tronic lanthanoid and actinoid species, e.g. Np(VI) and Ce(III), Np(V) and Pr(III), Np(IV) and Nd(III), are lower for the actinoids, indicating partial quenching of the orbital contribution by crystal field effects. 

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