Maser oscillations rely on the stimulated emission between two hyperfine energy levels of atomic hydrogen. This effect is analogous to the hyperfine structure in atomic spectra due to nuclear spin. The dominant term in the hyperfine Hamiltonian is typically the magnetic dipole term. This diagram indicates the electron Zeeman, nuclear Zeeman and hyperfine splittings. These emission lines correspond to much rarer atomic events such as hyperfine transitions. The methods mainly base on hyperfine interactions with the sourrounding atoms and ions. The hyperfine splitting in hydrogen, measured using Ramsey's hydrogen maser, is known with great precision. The lowest (hyperfine) energy level of H is nondegenerate. Sub-doppler techniques have been used to discern the hyperfine structure in HCN rotational transitions. Many measurements of magnetic moments and hyperfine structure followed. The optical hyperfine structure was observed in 1881 by Albert Abraham Michelson. The lowest transition (formula 49) splits into a hyperfine triplet. These methods use the interaction of the hyperfine field with the nucleus' spin. The effect is one type of hyperfine splitting. They then studied its hyperfine structure, gravity effects, and charge.