  By means of a canonical transformation it is shown how it is possible to
recast the equations for molecular nonlinear optics to completely eliminate
ground-state static dipole coupling terms. Such dipoles can certainly play a
highly important role in nonlinear optical response - but equations derived by
standard methods, in which these dipoles emerge only as special cases of
transition moments, prove unnecessarily complex. It has been shown that the
elimination of ground-state static dipoles in favor of dipole shifts results in
a considerable simplification in form of the nonlinear optical
susceptibilities. In a fully quantum theoretical treatment the validity of such
a procedure has previously been verified using an expedient algorithm, whose
defense was afforded only by a highly intricate proof. In this paper it is
shown how a canonical transformation method entirely circumvents such an
approach; it also affords new insights into the formulation of quantum field
interactions.
