From abstract: "In this paper the motion of a nucleus with an intrinsic quadrupole moment in an external electrostatic field gradient is discussed from a classical point of view. It is shown that in the classical approximation the angular momentum may precess about the direction of strongest field gradient or about the direction of intermediate field gradient, but not about the direction of weakest field gradient. The classical precession frequencies are found to be related to the quantum mechanical dipole transition frequencies."