1. Indications of the occurrence of fractional quantum numbers have already been found by Kratzer from a study of certain band spectra, and by Curtis in his experimental investigation of helium bands. Heisenberg has also employed half-integral numbers in a quantum theory of the anomalous Zeeman effect with considerable success. The fourth of the slightly extended quantum conditions recently suggested by W. Wilson and applied by the present writer to the Zeeman effect involves a fractional quantum number, as O. W. Richardson has pointed out. K. F. Niessen, in his work on the positively ionised hydrogen molecule, observes certain discontinuities in the energy graphs between symmetrical and asymmetrical models which strongly the occurrence of half-integral quantum orbits for the latter. He refrains, however, from making this assumption, on the ground that it would necessitate the adoption of half numbers in the somewhat allied case of the Stark effect.
Nobel Laureate Stormer to Give Plenary Talk on Fractional Quantum Numbers
