Landé interval rule

Landé interval rule

[län′dā ′int·ər·vəl ‚rül]
(atomic physics)
The rule that when the spin-orbit interaction is weak enough to be treated as a perturbation, an energy level having definite spin angular momentum and orbital angular momentum is split into levels of differing total angular momentum, so that the interval between successive levels is proportional to the larger of their total angular momentum values.