OPTICAL TRANSIENT BLEACHING OF PHOTOCHROMIC POLYTUNGSTIC ACID

The nonlinear optical properties of UV-coloured colloidal polytungstic acid imbedded in polyvinylalcohol film have been studied using a pico second pump-probe technique. The intervalence charge transfer bands in the red-near IR region were found to exhibit transient bleaching that decays monoexponentially with the characteristic time of similar to 3 00 ps. The results obtained are discussed in terms of the splitting of energy levels of metal ion in the ligand field and the delocalization of valence states. (C) 1998 Elsevier Science B.V. All rights reserved .