 It arises from dipolar coupling between two spin half nuclei, or from transitions in quadrupolar nuclei such as deuterium.It is the general shape obtained from an orientationally dependent doublet.The "horns" of the Pake doublet correspond to the situation when the principal axis of the coupling interaction (the internuclear vector in the case dipolar coupling and the principal component of the electric field gradient tensor for quadrupolar nuclei) is perpendicular to the magnetic field.