Molecular Rotation as Source for Magnetic Fields

Analogous to the rotational g tensor one defines a spin rotation tensor as the proportionality tensor between the rotational magnetic induction Rk, J) and the rotational angular momentum / (Gunther-Mohr et al, 1954 Flygare, 1964) 

The rotational magnetic induction, B [Rk,J), at the position of a nucleus K can be probed by the magnetic moment of this nucleus, like any other magnetic field within a molecule. The change in energy is then given by Eq. (5.50) 

Equation (6.46) explains also the name spin-rotation tensor for C, because it is the coupling tensor for the coupling of the rotational angular moment of the molecule J with the spin of the nuclei K, which gives rise to an additional contribution to the rotational energy. This is normally expressed in terms of an effective rotational Hamiltonian as 

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