In atomic physics, the Landé interval rule states that if the spin-orbit interactions of an electron are weak, the energy levels of each (i.e. the spin and orbit) are split. Subsequently, each have a different angular momentum. The rule states that as a result of this, the frequency interval between successive energy levels is proportional to the larger of their total angular momentum values (J).[1][2]


The rule assumes the Russell–Saunders coupling and that interactions between spin magnetic moments can be ignored. The latter is an incorrect assumption for light atoms. As a result of this, the rule is optimally followed by atoms with medium atomic numbers.[1]

The rule was first stated in 1923 by German-American physicist Alfred Landé.[1]


"Landé interval rule". Retrieved 10 October 2010.
Morris, Christopher G. (1992). Academic Press dictionary of science and technology. Academic Press. pp. 1201. ISBN 0-12-200400-0.

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