Two‐photon‐resonance four‐wave mixing for the study of permanent molecular dipoles

Two-photon-resonance four-wave mixing (TPR-FWM) spectroscopy was examined for the study of the permanent electric dipole moments of molecular states. A TPR-FWM process of the type ω4=ω1-ω2+ω3 in a three-state dipolar system was considered. The extraction of data for the difference in permanent dipole moments (Δμ) of states involved in TPR was analysed in the case of resonance TPR-FWM. Resonance TPR-FWM measurements were performed in a solution of the polydiacetylene poly-4BCMU. © 1998 John Wiley & Sons, Ltd.