Instrumentation for Laser Spectroscopy

作为先进材料、电信、生物技术和环境研究的主要举措的一部分，佐治亚理工学院（GT）正在建设一个世界级的时间分辨光谱设施。该设施将成为美国东南部现代时间分辨光谱学的核心，并将提供给佐治亚理工学院、佐治亚州立大学（GSU）和克拉克亚特兰大大学（CAU）的研究人员，后者是一所历史悠久的黑人大学。此核心组以外的用户的可用性将根据具体情况而定。Schuster教授和E1- Sayed教授从他们以前的大学搬来了最先进的皮秒和纳秒荧光寿命测量仪器，以及从皮秒到毫秒时间尺度的时间分辨吸收实验。这些仪器补充了GT和GSU现有的纳秒荧光和皮秒吸收光谱仪。此外，佐治亚理工学院还为时间分辨（3-5,us）傅里叶变换红外和拉曼光谱仪提供了资金。El-Sayed教授还将亚皮秒（~）移动了一倍。加州大学洛杉矶分校的5ps吸收光谱仪。然而，该仪器是基于锁模YAG激光器泵浦的染料激光器，其稳定性差和缺乏波长可调性限制了其实用性和可靠性。因此，美国国家科学基金会要求以50%的费用分摊水平提供资金，以完成激光光谱实验室的采购和安装一台基于钛蓝宝石的飞秒吸收光谱仪，包括时间分辨率为~ 100 fs的红外和共振拉曼测量能力。该仪器将位于新装修的空间，由全职激光光谱学家李松博士在Mostafa El-Sayed教授的指导下管理。宋博士还要求50%的工资支持。该设施还将通过国家资助的佐治亚电信技术中心补充现有的电信快速信号处理设施，并将与该中心的研究团体提供许多智力协同作用。目前，四个不同的团体将是所要求设备的主要用户。El-Sayed教授的主要用户组将阐明自然界中另一种光合系统细菌视紫红质（bR）将太阳能转化为电能的分子机制。在该系统中，光的吸收导致视网膜快速异构化，从而导致电荷分离、离子迁移、蛋白质构象改变以及质子从细胞内部向膜表面泵送，导致ADP转化为ATP。亚皮秒瞬态光学吸收和荧光设备将用于了解bR光合作用初级过程（视网膜光异构化）的蛋白质催化的分子起源，利用bR及其不同的突变体。在单独的研究中，光引发断键的飞秒动力学将被确定。Schuster的团队将研究DNA复合体中被取代的蒽醌辐照后产生的瞬态的性质，导致双链切割，并将研究氰酸盐中电子转移的动力学和能量学。托尔伯特的团队将研究“超级”光酸中的超快质子转移，以及聚甲基染料中的电荷迁移。Netzel的团队将研究DNA主干上芘发色团之间的能量和电子转移。Schwerzel建议研究胶体半导体中的能量和电子转移。虽然空间不允许详细的描述，但在电子和能量转移方面的进一步研究预计将由Dabney Dixon (GSU), Mark Mitchell （CAU）和Paul Wine （GT）的小组进行。

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).