Lande interval rule deviations from

The biquadratic exchange coupling constants adopt rather small values the experimental data show that exchange coupling constants obey j/J 0.05. The separation of the energy levels, however, alters significantly as the deviation from the Lande interval rule is dramatic for higher spin values [19]... 

In analogy with the magnetic dipole interaction constant a the electric quadrupole interaction constant b is a product of a nuclear quantity Q, the electric quadrupole moment, and an electronic quantity qj, which is proportional to the electric field gradient. Thus, with the b factor experimentally determined, information on the nucleus or the electronic shell can be obtained. The electric hyperfine structure is of the same order of magnitude as the magnetic one, but generally somewhat smaller. It exhibits itself as a deviation from the Lande interval rule. In Fig.2.18 two examples of the combined action of magnetic and electric hyperfine structure are shown. 

The repulsion between singlet and triplet F=I states is indi cated by comparison between Fig. 5a and b. As can be seen from Eqs.(4), the singlet-triplet mixing causes a shift of the F=3/2 component from the position predicted by the Lande interval rule. Using the F=1/2 to 5/2 splitting these positions were calculated and their deviation from the actually measured ones is plotted in Fig. 5b as a function of n. The data for the series approximate-... 

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