splitting of a spectral line of an atom or molecule into two or more closely spaced components as a result of interaction of the electrons with the magnetic moments of the nuclei
See full dictionary entry for hyperfine
hyperfine structure in British English
(ˈhaɪpəˌfaɪn)
noun
the splitting of a spectral line of an atom or molecule into two or more closely spacedcomponents as a result of interaction of the electrons with the magnetic moments ofthe nuclei