GROUND AND EXCITED-STATE DIPOLE-MOMENTS OF COUMARIN LASER-DYES - INVESTIGATION BY ELECTROOPTICAL ABSORPTION AND EMISSION METHODS

Modified electro-optical absorption and emission methods were used to measure the dipole moments of four efficient coumarin laser dyes (CU1, CU4, CU120, CU334) in the equilibrated ground, excited Franck-Condon and equilibrated excited states. The measurements were performed in cy clohexane (CU1, CU120, CU334) and dioxane (all CUs) at room temperatur e. Our results show that the charge distribution in CU4 differs substa ntially from that in the other CUs. The equilibrated ground and excite d state dipole moments measured by electro-optical methods are compare d with those derived from other measurement techniques and from semiem pirical calculations. The possible role of twisted intermolecular char ge transfer (TICT) state formation is discussed.