Light Induced Processes in the Condensed Phase

这项研究主要集中在光学和红外飞秒脉冲产生和近场显微镜这两个最近技术进步引起的主要领域。材料在太赫兹和振动基区的线性和非线性红外特性现在可以在40-160 fs范围内用时间分辨率获得。这些方法将用于在宽频率范围内直接测定共轭聚合物、电荷转移配合物及其晶体中电荷重组的核反应。核运动的脉冲激发产生波包，其随时间的运动可以用来表征所涉及的势面。振动能量动力学也将直接研究。本文将对聚硅烷线性链上受约束激发的材料的高激子态进行完整的研究，以了解电子和空穴更分离的这种链的激发态。提出的研究的第二个领域是使用近场方法关注有机纳米级系统的动力学和电子特性。要表征的材料包括：自组装的单层蛋白质（在半导体上），可以进行能量和电子转移，具有单个蛋白质的空间分辨率；可以分别考察线性链激励的聚硅烷薄膜和拉伸薄膜；具有相干长度大于近场显微镜尖端尺寸的菁染料聚集体；有机纳米粒子可以单独检测，并表征其约束特性。我们提出的研究主要集中在光学和红外飞秒脉冲产生以及近场显微镜两个主要领域。第一个涉及表征飞秒振动和电子响应的材料在光谱的红外区域，从接近零频率到8000厘米-1。二是利用新发展的近场皮秒时间分辨显微技术测定纳米和低维有机、生物和高分子材料的光学性质。这项工作很重要，因为：1)材料，特别是有机和生物材料的红外特性尚未被广泛探索；2)它允许在单个分离分子的尺度上检查材料中的纳米环境。

9421043 Hochstrasser This research is focused on two main areas arising from recent technological advances in optical and infrared femtosecond pulse generation and near-field microscopy. Linear and nonlinear infrared properties of materials in the teraherz and the vibrational fundamental region are now accessible with time resolution in the 40-160 fs regime. These methods will be used to determine directly the nuclear responses, over a wide frequency range, to charge reorganization in conjugated polymers, charge transfer complexes and their crystals. Impulsive excitations of the nuclear motions leads to wavepackets whose motion in time can be used to characterize the potential surfaces involved. The vibrational energy dynamics also will be studied directly. A complete study of the higher exciton states of materials with confined excitations on linear chains of polysilanes will be conducted to understand the excited states of such chains in which the electron and hole are more separated. The second area of the proposed research is concerned with the dynamics and electronic properties of organic nanoscale systems using near-field methods. The materials to be characterized include: self assembled monolayers of proteins (on semiconductors) that can undergo energy and electron transfer with single protein spatial resolution; polysilane films and stretched films in which linear chain excitations can be separately examined; aggregates of cyanine dyes having coherence lengths larger than the tip size of the near-field microscope; and organic nanoparticles that can be separately examined and their confinement properties characterized. %%% The proposed research is in two main areas arising from our recent technological advances in optical and infrared femtosecond pulse generation and near-field microscopy. The first involves characterization of the femtosecond vibrational and electronic responses of materials in the infrared region of the spectrum from close to zero frequency to 8000 cm-1. The second is the determination of optical properties of nanoscopic and low dimensional organic, bio and polymeric materials by means of the newly developed near- field picosecond time resolved microscopy. This work is important because: 1) infrared properties of materials, particularly organic and biomaterial are not widely explored yet, and 2) it allows examining nanoenvironment in materials on the scale of single, isolated molecule.