Laser perturbation of an atom with fine or hyperfine structure is analyzed. The use of sufficiently powerful, or spectrally broad light produces effects, which form an optical analogue to the Back--Goudsmit effect. Such laser decoupling of hyperfine interaction is easily understood in terms of an analogy of the level-crossing effect and the double-slit experiment. The consequences of the optical Back--Goudsmit effect for efficiency of optical pumping in ³He are discussed.

PACS numbers: 32.80.--t, 42.50.Hz