spectroscopic and computational 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)使用团簇光谱研究掺杂探针分子的类氢团簇；b)应用氦纳米液滴光谱在微观水平上研究化学反应。啁啾脉冲宽带傅里叶变换微波光谱仪的构建将促进含团簇的对氢分子的旋转光谱分析。由此产生的光谱参数将被分析，以检测和跟踪从分子微观状态的整体特性，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。我们将利用新构建的氦纳米液滴光谱仪，研究包含数千个氦原子的氦液滴中嵌入的物质的光诱导化学反应。氦纳米液滴在这里充当微观反应器和量热计。在红外、太赫兹和微波波段对掺杂氦纳米液滴进行进一步的光谱研究将有助于我们理解掺杂-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 study paraHydrogen clusters doped with a probe molecule and b) to apply helium nanodroplet spectroscopy to the study chemical reactions on the microscopic level. Rotational spectroscopy of paraHydrogen molecules containing clusters will be facilitated by the construction of a chirped pulse broadband Fourier transform microwave spectrometer. The resulting spectroscopic parameters will be analyzed to detect, and 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 photo-induced chemical reaction of species embedded in helium droplets that contain several thousand helium atoms. The helium nanodroplets serve here as microscopic reactor and calorimeter. Further spectroscopic studies on doped helium nanodroplets 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.