Studies of intermolecular interactions

分子间相互作用在许多领域都很重要，包括冷凝和蒸发等过程，凝聚态物质的性质，蛋白质折叠和分子识别等生物过程，以及自组装。本提案通过分子聚集体的表征来描述分子间相互作用的研究，从包含几个分子的小复合物到由几千个原子组成的大纳米团簇，使用最先进的高分辨率光谱技术。两个主要的创新方向是：a)利用簇光谱探索微观、分子世界和体相之间的桥梁；b)将氦纳米液滴分离光谱应用于新化学物质的研究。用微波傅立叶变换光谱仪研究了含簇的氦原子和氢分子的旋转光谱。由此产生的光谱参数将用于跟踪从分子微观状态的体性质，即超流动性的演变。这些研究将被He -分子和H2 -分子二聚体的高水平从头计算和随后的束缚态计算所补充。二聚体的理论结果将为更大簇的实验研究提供一个重要的起点。我们将使用我们新建造的氦纳米液滴光谱仪来研究包含数千个氦原子的氦液滴中嵌入的物种。这些在红外、太赫兹和微波区域的光谱研究将有助于我们理解掺杂剂-氦液滴的相互作用，以及氦液滴本身的有趣性质。

Intermolecular interactions are of importance in many areas, including processes such as condensation and evaporation, properties of condensed phase matter, biological processes such as protein folding and molecular recognition, and self assembly. This proposal describes study of intermolecular interactions by the characterization of molecular aggregates, from small complexes that contain a few molecules to large nano-clusters that consist of several thousand atoms, using state-of-the-art high resolution spectroscopic techniques. The two major innovative thrusts are: a) to use cluster spectroscopy to explore the bridge between the microscopic, molecular world and the bulk phase and b) to apply helium nanodroplet isolation spectroscopy to the study of novel chemical species. Rotational spectra of helium atoms and hydrogen molecules containing clusters in the intermediate size regime will be studied using our microwave Fourier transform spectrometer. The resulting spectroscopic parameters will be used to follow the evolution of a bulk property, namely superfluidity, from the molecular, microscopic regime. These studies will be complemented by high level ab initio calculations of He - molecule and H2 - molecule dimers and subsequent bound state calculations. The theoretical results on the dimers will provide an important starting point for the experimental investigations of the larger clusters. We will use our newly constructed helium nanodroplet spectrometer to investigate species embedded in helium droplets that contain several thousand helium atoms. These spectroscopic studies in the infrared, Terahertz, and microwave regions will contribute to our understanding of the dopant - helium droplet interaction and also of the interesting properties of the helium droplets themselves.