ABSORPTION, LUMINESCENCE, RESONANCE RAMAN, AND RESONANCE CARS SPECTROSCOPY ON FBS DIACETYLENE SINGLE-CRYSTALS WITH COLOR ZONES

We have made investigations on color zones in FBS diacetylene single crystals by means of various optical spectroscopical methods in order to derive a plausible model for the origin of this type of chromism. Absorption, luminescence, resonance Raman, and CARS spectroscopy revealed that most probably growth defects in {111} crystal growth sectors influence the side group geometry of FBS polymer chains. This results in shortening of the pi-electron conjugation lengths and in consequence in an anti-Stokes shift of electronic and vibrational transition frequencies. Particularly, resonance CARS spectroscopy proves to be a new valuable tool for the investigation of electronic and structural properties of the FBS crystals.