Hole Burning Studies of Electric Fields in Organic Solids

在化学学部物理化学项目中，加州大学河滨分校的Bryan E. Kohler教授将使用孔燃烧光谱技术对有机固体中的电场进行研究。以往在测量和解释外电场对跃迁能的影响方面取得的成功，为本文提出的在分子系统中分子位点绘制内电场的研究奠定了基础。具体来说，电场对线性多烯激发能的影响，以及外部压力对电场对线性多烯激发能的影响，将被确定为许多不同的主客系统，其中几何结构可以通过标准分子动力学技术计算。通过测量和理论模拟的结合，更复杂的系统将成为可用于研究的解释模型的细化。用于确定内部电场的大多数理论模型假设点偶极近似，这被发现只是定性成功。本研究的目的是通过实验测量多烯掺杂烷烃晶体的场。我们对有机固溶体的电子结构的认识大多来自于光谱学。如果所研究的系综更加均匀，可以从给定的光谱中提取的明确信息的数量就会增加。这可以通过几种高分辨率位点选择光谱方法中的一种来完成，例如，孔燃烧光谱。通过这种技术，分辨率提高了十万倍。这反过来又使弛豫过程的研究成为可能，例如，光学减相和光谱扩散；有机固体中的能量传递；生物系统光物理过程的表征；有机聚合物在光学数据存储和全息技术中的应用和其他人。在这个项目中进行的研究将有助于更好地理解不同固体有机系统中的光学过程，并可能导致光学和电子器件中使用的材料的改进。

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.