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The investigation of multichromophore-containing electro-optic dendritic material demonstrates that the frequently observed asymptotic dependence of electro-optic activity on chromophore number density might be overcome through rational design.

A novel approach is developed to simultaneously achieve high first-order hyperpolarizability [beta] values while providing an adjustable dipole moment by linking a strong neutral-ground-state (NGS) nonlinear optical (NLO) chromophore with positive [beta] to a zwitterionic (ZWI) chromophore with negative [beta] in an antiparallel fashion. The results have shown that an antiparallel-aligned NGS chromophore and a zwitterionic chromophore can simultaneously achieve an increase in [beta] and a decrease of the dipole moment.

A series of nonlinear optical (NLO) chromophores incorporating the ferrocenyl (F) group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl 1-2,5-dihydrofuran (TCF) derivatives as electron acceptors is discussed. The excellent agreement between the theoretical and experimental beta values demonstrates that a linear relation exists between the hyperpolarizability and the bond length alteration.

Femtosecond transient absorption spectroscopy was used to study the photochemistry of chlorine dioxide in aqueous solution.

Picosecond, time-resolved UV stokes and anti-stokes resonance Raman spcetroscopy were used to establish the photoproduct development, conformational kinetics and vibrational relaxation kinetics in the photochemical ring-openings of 1,3-cyclohexadiene (CHD) and alpha-phellandrene (alpha-PHE), and experiments were conducted on the transformation of alpha-PHE to 3,7-dimethyl-1,3,5-octatriene (OT) and of CHD to cis-hexatriene (c-HT). The photoproduct anti-stokes ethylenic intensity in both reactions decays in nine plus or minus two ps, and has a time constant of eight plus or minus two ps, suggesting that the intermolucular vibrational relaxation kinetics and the emergence of the photoproduct are not significantly influenced by the existence of alkyl substituents.

The time-resolved electron paramagnetic resonance spectroscopy is employed to explain the properties of the triplet states of the nonlinear optical chromophore 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) in single crystals of potassium hydrogen phthalate. The relationship between these triplet states and the single-molecule dark states is also explained.

Two new highly hyperpolarizable chromophores, based on N,N-bis-(4-methoxyphenyl)aryl-amino donors and phenyl-trifluoromethyl-tricyanofuran (C[F.sub.3]-Ph-TCF) acceptor linked together through [pi]-configuration through 2,5-divinylenethienyl moieties as the bridge, are designed and synthesized. The studies have helped in understanding the effects on molecular hyperpolarizability of substituting heteroaromatic subunits into the donor groups structures.

A series of novel nonlinear optical (NLO) chromophores 1-4 incorporating the ferrocenyl (Fc) group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran (TCF) derivatives as electron acceptors are presented. The use of a constant Fc donor and varied acceptors and bridges makes it possible to systematically determine the contribution of the conjugated bridge and the acceptor strength to chromophore nonlinear optical activity. The X-ray crystal structures of all four chromophores allow for the systematic investigation of the structure-property relationship for this class of molecules. For example, the crystal structures reveal that both cyclopentadienyl groups in the ferrocenyl donor contribute to the electron donating ability. The first-order hyperpolarizabilities beta of these chromophores, measured by hyper-Rayleigh scattering (HRS) relative to p-nitroaniline are reported. These beta values are compared to those calculated by density functional theory (DFT). The excellent agreement between the theoretical and experimental beta values demonstrates that a linear relation exists between the hyperpolarizability and the bond length alternation. An electrooptic coefficient, r(33), of approximately 25 pm/V at 1300 nm, for compound 4, incorporated into a polymer matrix, is competitive with organic chromophores. Moreover, this r(33) is more than 30 times larger than the previously reported value for an organometallic chromophore in a poled polymer matrix. This work not only underscores the potential for Fc donor moieties, which have been underutilized, but also demonstrates that experimental characterization and theoretical simulations are now congruent, viable methods for assessing potential performance of NLO materials.