Spectroscopic Investigations of the Mechanisms of Energy Transfer in Luminescent Crystals and Photolysis of Atmospheric Molecules

Our main interest is the spectroscopic studies for to the energy transfer processes in luminescent crystals and the photolysis of atmospheric chemistry species. This proposal is an extension of our accomplishments, and the related publications are expected after some experimental data are completed and confirmed. For luminescent crystals, spectroscopic data such as photoluminescence, excitation, and time-resolved spectra are acquired to elucidate the energy transfer processes between luminescent centers containing trivalent rare earth elements. Detailed mechanisms and accurate kinetics models were developed. These models fit experimental data of compounds containing Eu3+ perfectly, but there still remain unresolved questions in the Sm3+-containing compounds. We will unravel the details of these energy processes and the results will pave the foundation for developing display technology and solar cells. In atmospheric chemistry, the formation mechanisms of highly excited halogens following the photolysis of halomethanes at ultraviolet wavelengths are currently studied. Our results indicate that in spite of their similar spectra, highly excited atomic bromine and atomic iodine have very different formation mechanisms. The detailed differences will be clarified in this proposal. Additionally, we also plan to study the electronic spectroscopy of CI2, which is related to the formation of highly excited iodine and is a challenging subject in molecular spectroscopy. This part of our research is for pure scientific interest, but will help to understand the fundamental gas-phase photolysis. In collaboration with other research groups, we have been developing new non-linear optical (NLO) materials such as second harmonic generation (SHG) crystals. In 2016, we found new lithium-containing titanosilicates that have excellent phase-matched SHG signals and high laser-induced damage threshold. The results were published on J. Am. Chem. Soc., and the related patents are approved in Taiwan as well as in the U.S. We plan to investigate the detailed correlations between the crystal structure and SHG properties. A theoretical model of the SHG-structure correlation is also under development.