Spectroscopic Studies of Clusters and Aggregates

该研究计划描述了一个程序，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大小范围内的物质。这些研究在很大程度上是由高分辨率光谱学的革命，无论是在新的，更强大的光谱技术的发展和其成功应用到越来越大的分子系统。在中等大小的制度，我们建议研究团的氦原子，和那些氢分子，掺杂分子发色团，如一氧化碳或氰化氢。这些结果将进一步阐明体相性质，即超流性，是如何从微观尺度演变的。超流性是组成粒子的玻色子（整数复合自旋）特性的结果。我们特别感兴趣的是使用费米3-氦和HD作为溶剂物种。在这些情况下检测超流体效应将挑战当前的解释。我们新研制的啁啾脉冲傅里叶变换微波光谱仪将使这些研究成为可能。更大的氦纳米液滴，可以由大约一千到数百万个氦原子组成，将作为纳米低温恒温器和纳米反应器，用于研究具有大气和天体物理重要性的低温反应。重点将放在无障碍反应，如碳链延长反应涉及碳原子和羟基自由基反应。反应性物质将通过激光烧蚀或激光诱导的前体（例如过氧化氢）的光解离来产生。第三个研究领域涉及更大聚集体的形成，即二次有机气溶胶（“烟雾”）。这些气溶胶可能对气候和人类健康产生重大影响。我们的研究将有助于改进大气化学模式。

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.