The magnetic field dependence of the isotropic nonrelativistic one‐electron atom with nuclear spin‐1/2, in its electronic ground state, is reviewed. Attention is called to the little‐known fact that a level crossing exists (at field B∼17 T for 1H) between the two members of the upper spin (MS=1/2) doublet. Anisotropy of such a hydrogenic atom, due to the presence of a suitable external electric field (for instance, 1H trapped in crystalline SiO2) causes anticrossing of these levels and causes previously forbidden magnetic‐dipole transitions to attain appreciable intensity in that B region.

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