The Structures of the Ground Multiplets of Certain Rare-Earth Ions

Abstract

Departures from the Landé interval rule in the ground multiplets of certain rare-earth ions are examined. It is found that magnetic spin-spin interactions between the 4f electrons are much too small to account for the apparent distortions, but that by allowing for the partial breakdown of Russell-Saunders coupling it is possible to obtain satisfactory agreement between experiment and theory. Values of the spin-orbit constant ζ are given for several rare-earth ions, and the positions of a number of excited multiplets are tabulated.