A general pattern of the nuclear magnetic resonance spectrum of a molecule AX, where A and X are both spin-½ nuclei. If X is spin α, the spin-spin interaction between the nuclei of A and X results in one line in the spectrum of A being shifted by J/2 from the frequency of precession it has in the absence of coupling. If X is spin β, the change in frequency of precession of A is –J/2. Thus, single lines in the resonances of both A and X are split into doublets, with splittings J. The A resonance in molecules of the type AnX is also a doublet with the splitting J.