In the present work, we have studied modifications in the transition and permanent dipole moments of states in a coupled basis (including vibronic coupling) due to variations in the transition dipole moment between the uncoupled states, m12, as a function of the parameter δ = ω̃0/ω0 (relative aperture) of the potential-energy curves of the states involved. Modifications in the slopes of the transition and permanent dipole moments of the coupled states and changes in the magnitude of maximal intensity of the four-wave mixing (FWM) signal are observed due to variations in these parameters. © 2004 Wiley Periodicals, Inc.