Investigations of Atmospheric Intermediates and Solid-State Crystals Using Spectroscopic Techniques

We have applied spectroscopy techniques to investigate the spectroscopy and kinetics related to atmosphericchemistry and luminescent crystals. In atmospheric chemistry, the formation mechanisms of highly excitedhalogens in the photolysis of halomethanes at ultraviolet wavelengths are of interest. Our results indicate thatin spite of their similar spectra, atomic bromine and atomic iodine have different formation mechanisms. Thedetailed mechanisms will be clarified in this proposal. Additionally, we also plan to study the spectroscopy ofrelated dihalo-carbenes such as CBr2 and CI2. This proposal will also focus on the energy transfer processesin molecules containing trivalent rare earth elements including mechanisms, rates, and efficiency usingphotoluminescence spectroscopy, excitation spectra, and time-resolved spectroscopy. Accurate kineticsmodels were developed and fit experimental data of compounds containing Eu3+ perfectly, but there stillremain unresolved questions in the Sm3+-containing compounds. We will elucidate the details of these energyprocesses and the results will pave the foundation for developing related technology. In collaboration withother research groups, we have been studying the non-linear optical (NLO) properties such as secondharmonic generation (SHG) in inorganic and organic materials. New lithium-containing titanosilicates werefound to have excellent phase-matched SHG signals and high laser-induced damage threshold. The resultswere published on the top journal, J. Am. Chem. Soc., and related patent applications are pending approval.We plan to investigate the detailed correlations between the crystal structure and SHG properties. Atheoretical model of the SHG-structure correlation is also under development.