Theoretical Prediction, Synthesis and Characterization of RSA materials

We propose to synthesize and characterize by time resolved spectroscopy RSA compounds that have been structurally modified to maximize the ratio of excited state to ground state absorption cross sections over a broad visible range. The structuralmodifications will be made based on ab initio and semiempirical quantum mechanical predictions of excited state energetics and absorption intensities. The theoretical models will be developed by the Mark Ratner group at Northwestern, based on our priorcollaborations resulting in accurate prediction of triplet-triplet absorption energies in over 100 organic chromophores, in effect allowing a priori predictions of wavelength-dependent optical limiting curves in hypothetical molecules. The results of PhaseI provided a promising new series of strong optical limiters based on the triplet-triplet absorption spectra, with the onset of nonlinearity at <10-8 J input fluence, as well as insights to the structural effects using density functional theory and ZINDO.Phase II will address the optimization of the optical protection systems and their incorporation into suitable thin solid matrices for use in intermediate focal plane optical assemblies and eyewear.The general materials approach will enable rapiddevelopment of new optical limiting materials for the full range of threat wavelengths. The materials have government markets for sensor and eye protection and commercial markets as laser safety eyewear and as protection for cameras and opticalinstruments. Additional markets for active glare reduction and for photodynamic therapy are anticipated for the new materials.