Spectroscopic Studies of Clusters and Aggregates

该研究计划描述了一个项目，通过分子聚集体的表征来研究从微观、分子世界到纳米尺度的物质大小。这些研究在很大程度上得益于高分辨率光谱学的一场革命，无论是在开发新的、更强大的光谱技术方面，还是在成功应用于更大的分子系统方面。在中等大小的体系中，我们建议研究氦原子团簇和氢分子团簇，掺杂分子发色团，如一氧化碳或氰化氢。结果将进一步阐明体相性质，即超流动性，是如何从微观尺度演变而来的。超流动性是组成粒子的玻色子（整数复合自旋）特性的结果。我们对使用费米子3-氦和HD作为溶剂特别感兴趣。在这些情况下发现超流体效应将挑战目前的解释。我们新建立的啁啾脉冲傅立叶变换微波光谱仪将使这些研究成为可能。

The research proposal describes a program to study matter in size regimes from the microscopic, molecular world to the nano-scale by the characterization of molecular aggregates. These studies are largely enabled by a revolution in high resolution spectroscopy both in terms of the development of new, more powerful spectroscopic techniques and its successful application to ever larger molecular systems. In the intermediate size regime, we propose to study clusters of helium atoms, and those of hydrogen molecules, doped with molecular chromophores, such as carbon monoxide or hydrogen cyanide. The results will shed further light on how a bulk phase property, namely superfluidity, evolves from the microscopic scale. Superfluidity is a consequence of the bosonic (integer composite spin) character of the constituent particles. We are particularly interested in using the fermionic 3-helium and HD as solvent species. The detection of superfluid effects in these cases would challenge current interpretations. Our newly constructed chirped pulse Fourier transform microwave spectrometer will make these studies possible. Much larger helium nanodroplets, which can consist of about a thousand to millions of helium atoms will serve as nano-cryostats and nano-reactors for the study of low temperature reactions of atmospheric and astrophysical importance. Emphasis will be on barrier-less reactions, such as carbon chain lengthening reactions involving carbon atoms and hydroxyl radical reactions. The reactive species will be produced by laser ablation or laser induced photodissociation of a precursor, such as hydrogen peroxide. A third research area concerns the formation of even larger aggregates, namely secondary organic aerosols ('smog'). These aerosols can have significant effects on climate and human health. Our studies will contribute to the improvement of atmospheric chemistry models.