As part of major initiatives in advanced materials, telecommunications, biotechnology, and environmental research, Georgia Institute of Technology (GT) is building a world-class timeresolved spectroscopic facility. This facility will form the nucleus of modern time-resolved spectroscopy in the Southeast, and will be available to researchers at Georgia Tech, Georgia State University (GSU), and Clark Atlanta University (CAU), a historically black university. Availability to users outside this core group will be on a case-by-case basis. Professors Schuster and E1- Sayed have moved instruments from their former universities for state-of-the-art measurements of picosecond and nanosecond fluorescence lifetimes as well as for time- resolved absorption experiments ranging from picosecond to millisecond timescales. These complement existing instruments for nanosecond fluorescence and picosecond absorption spectrometers available currently at GT and GSU. In addition, Georgia Tech has provided funds for time- resolved (3-5, us) Fourier transform infrared and Raman spectrometers. Prof. El-Sayed has also moved a subpicosecond (~ . 5 ps) absorption spectrometer from UCLA. However, this instrument is based upon a dye laser pumped by a mode-locked YAG laser, and its poor stability and lack of wavelength tunability limit its utility and reliability. Therefore, funds on a 50% cost sharing level are requested from NSF to complete the laser spectroscopy laboratory by the acquisition and installation of a Ti-sapphire-based femtosecond absorption spectrometer, including capabilities for infrared and resonance Raman measurements with a time resolution of ~ 100 fs. This instrumentation will be located in newly renovated space and will be managed by a full-time laser spectroscopist, Dr. Li Song, under the direction of Prof Mostafa El-Sayed. Salary support at a 50% level is also requested for Dr. Song. This facility will also complement existing facilities for fast signal processin g in telecommunications through the Georgia Center for Telecommunications Technology, funded by the state, and will provide much intellectual synergism with the research community at that center. At the moment, four different groups will be major users of the requested equipment. The primary user group of Prof. El-Sayed will eludicate the molecular mechanisms of the solar-to-electric energy conversion by the other photosynthetic system in nature, bacteriorhodopsin (bR). In this system, the absorption of light leads to rapid retinal isomerization which results in charge separation, ion migration, protein conformation changes, and proton pumping from inside the cell to its membrane surface, leading to the conversion of ADP into ATP. The subpicosecond transient optical absorption and fluorescence equipment will be used to understand the molecular origin of the protein catalysis of the primary process (the retinal photoisomerization) of bR photosynthesis, using bR, and its different mutants. In separate studies, femtosecond dynamics of photoinitiated bond-breaking will he deterrnined. Schuster's group will study the nature of transients produced upon irradiation of substituted anthraquinones in DNA complexes, leading to double strand cleavage, and will also investigate the dynamics and energetics of electron- transfer in cyanine borates. Tolbert's group will study ultrafast proton transfer in "super" photoacids, as well as charge migration in polymethine dyes. Netzel's group will study energy and electron transfer between pyrene chromophores on a DNA backbone. Schwerzel proposes studies of energy and electron transfer in colloidal semiconductors. Although space does not permit detailed descriptions, additional studies in electron and energy transfer are anticipated by the groups of Dabney Dixon (GSU), Mark Mitchell (CAU), and Paul Wine (GT).
