Hole Burning Studies of Electric Fields in Organic Solids

在化学系物理化学计划的这个项目中，加州大学河滨分校的布莱恩·E·科勒教授将利用烧孔光谱技术研究有机固体中的电场。前人在测量和解释外加电场对跃迁能影响方面的成功，是绘制分子系统中分子位置的内部电场图的基础。具体地说，电场对线性多烯激发能的影响，以及外压对电场对线性多烯激发能影响的影响，将被确定为一些不同的客体-宿主系统，其中几何构型可以用标准分子动力学技术计算。随着通过测量和理论模拟相结合的解释模型的改进，更复杂的系统将变得可供研究。大多数用于确定内部电场的理论模型都假设点偶极子近似，这被发现只是定性地成功的。所提出的研究旨在使用多烯掺杂的烷烃晶体来实验测量电场。我们对有机固溶体的电子结构的大部分理解都来自于光学光谱学。如果被研究的系综变得更加均匀，可以从给定的光谱中提取的明确信息量就会增加。这可以通过高分辨率位置选择光谱学的几种方法之一来完成，例如，烧孔光谱学。利用这项技术，分辨率提高了高达10万倍。这反过来又使得对弛豫过程的研究成为可能，例如，光学退相和光谱扩散；有机固体中的能量传递；生物系统中光物理过程的表征；有机聚合物在光学数据存储和全息照相中的应用；以及其他。本项目将进行的研究将有助于更好地了解各种固体有机系统中的光学过程，并可能导致改进用于光学和电子设备的材料。

In this project in the Physical Chemistry Program of the Chemistry Division, Prof. Bryan E. Kohler of the University of California at Riverside will engage in a study of electric fields in organic solids using the technique of hole burning spectroscopy. Previous successes for measuring and interpreting the effects of external electric fields on transition energies are the bases for the proposed research to map out the internal electric fields at a molecular site in a molecular system. Specifically, the effets of electric fields on linear polyene excitation energy, and the effect of external pressure on the effect of electric field on linear polyene excitation energy, will be determined for a number of different guest-host systems where the geometry can be calculated by standard molecular dynamics techniques. More complex systems will become available for investigation with the refinement of the interpretative model through a combination of measurement and theoretical simulation. Most theoretical models used for the determination of internal electric fields assume the point dipole approximation, which is found to be only qualitatively successful. The proposed investigations are designed to experimentally measure the fields using polyene doped alkane crystals. Much of our understanding of electronic structure of organic solid solutions is derived from optical spectroscopy. The amount of unambiguous information that can be extracted from a given optical spectrum is increased if the ensemble under investigation is made more homogeneous. This may be done by one of several methods of high resolution site selective spectroscopy, e.g., hole burning spectroscopy. With this technique resolution enhancements by a factor of up to one hundred thousand have been achieved. This in turn has allowed the investigations of relaxation processes such as, for example, optical dephasing, and spectral diffusion; energy transfer in organic solids; the characterization of photophysical processes in biological systems; applications of organic polymers to optical data storage and holography; and others. The research to be conducted in this project will contribute to a better understanding of optical processes in diverse solid organic systems and may lead to improved materials used in optical and electronic devices.