In paramagnetic compounds, the hyperfine interactions between the 2H nuclei and electron spins in paramagnetic ions should be incorporated to the Hamiltonian of Eq. (1). Neglecting the isotropic component from the Fermi- and pseudo-contact interactions, the hyperfine interaction can be given by the dipole coupling of nuclear–electron spins as
.
The term RQ 2;0 represents
the spatial orientation of the electric field gradient (EFG) tensor
with respect to static magnetic field. In the presence of molecular
motion, the tensor orientation may be transformed from the principal
axis system (PAS) to the laboratory frame by several steps,
which is expressed by