Scattering by Strong Long-Range Forces, Quantum Superposition States of Nanoscale Objects: Exploring Quantum Rrocesses with the Use of Atomic Clusters

本研究项目利用大量选择原子纳米团簇光束的实验技术和能力，研究两种既具有基本特征又具有重要实际意义的量子现象。第一个主题涉及“大永久偶极子”的长程势对非弹性碰撞的影响。具体来说，电子捕获的绝对横截面将被一个非常强的电偶极子场首次测量。此外，一个巨大的磁偶极子对捕获过程迄今未探索的影响将被探索。原子簇是这种测量的唯一合适目标。该项目的第二部分将确定存在于纳米尺度上的新型量子共振：处于两个几何形状的量子线性叠加状态的团簇粒子。这种鉴定将通过具有明确尺寸和同位素组成的自由金属团簇的激光光谱来完成。显示电子壳结构的尺寸选择金属团簇的光学光谱。“人造原子”)将用于检测它们的同位素质量对集体电子共振吸收的影响。这种奇特的同位素效应将揭示纳米尺度领域中存在一种新的量子共振现象：团簇形状构型的量子叠加。原子团簇是由有限数量的原子组成的纳米级聚集体，从几个到数千个不等。它们在一端连接单个原子和分子，另一端连接较大的粒子（如微结构和气溶胶）和大块材料。精确调整簇大小和组成的能力使人们能够制备具有有用和不寻常特征的量子大小的物体，并研究与这些特征相关的新物理现象。在这个项目中使用的一个特性是，某些簇能够在其附近产生极强的电场和磁场，并利用这些磁场吸引和捕获附近的带电粒子，例如电子。该项目将测量这一过程的效率，迄今为止从未探索过与“极地”集群产生的磁场强度一样高的磁场强度。除了提供新的基本见解外，这些结果还将对理解超冷分子和离子的相互作用、实现通过外部应用场控制化学反应的目标、磁性纳米粒子的研究以及理解大气和星际环境中发生的过程具有实际意义。在该项目的第二部分，将研究纳米团簇执行量子形状振荡的能力，换句话说，同时处于两种不同形状的量子叠加状态。这一实验观察将揭示在纳米尺度上出现的量子行为的一个新的和独特的情况。该研究还与核物理学和超冷原子云物理有很强的概念重叠，并可能在光学纳米电子学中有应用。在人力资源方面，该项目将为研究生提供跨学科领域广泛的实验和理论方面的优秀培训。博士后研究人员将接受专业指导。对教学和推广的承诺包括持续积极的本科生参与研究，以及对大学项目、科学博览会和国内外本科生研讨会的贡献。

This research project employs the experimental techniques and capabilities of beams of mass-selected atomic nanoclusters to investigate two types of quantum phenomena, both of fundamental character but also of important practical significance. The first subject involves the influence of long-range potentials 'those of large permanent dipoles' on inelastic collisions. Specifically, absolute cross sections for electron capture by a very strong electric dipole field will be measured for the first time. In addition, the heretofore unexplored influence of a giant magnetic dipole on the capture process will be explored. Atomic clusters represent uniquely suitable targets for such measurements. The second part of the project will identify a novel quantum resonance existent at nanoscale dimensions: a cluster particle in a state corresponding to a quantum linear superposition of two geometric shapes. This identification will be accomplished via laser spectroscopy of free metal clusters with a well-defined size and isotopic composition. Optical spectroscopy of size-selected metal clusters exhibiting electronic shell structure (a.k.a. "artificial atoms") will be used to detect the influence of their isotopic mass on the collective electron resonance absorption. This peculiar isotope effect will reveal the presence of a novel quantum resonance phenomenon in the nanoscale domain: quantum superposition of cluster shape configurations.Atomic clusters are nanoscale aggregates made up of a finite number of atoms, from a few to thousands. They bridge the gap between individual atoms and molecules on one end, and larger particles (such as microstructures and aerosols) and bulk materials on the other. The ability to adjust precisely the cluster size and composition allows one to prepare quantum-size objects with useful and unusual features, and to investigate novel physical phenomena associated with these features. One property, utilized in this project, is the capability of certain clusters to generate extremely strong electric and magnetic fields in their vicinity, and to use these fields to attract and capture nearby charged particle, e.g. electrons. The project will measure the efficiency of this process, heretofore never explored for field intensities as high as those generated by the "polar" clusters. In addition to providing new fundamental insight, the results will have practical implications for understanding the interactions of ultracold molecules and ions, for the goal of achieving control of chemical reactions by externally applied fields, for investigation of magnetic nanoparticles, and for understanding processes occurring in atmospheric and interstellar environments. In the second part of the project, the ability of nanoclusters to execute quantum shape oscillations in other words, to be in a quantum superposition of two different shapes at the same time will be investigated. This experimental observation will reveal a new and distinctive case of quantum behavior appearing at the nanometer length scale. This research also has a strong conceptual overlap with nuclear physics and with the physics of ultracold atomic clouds, and may have applications in optical nanoelectronics. On the human resources side, the project will offer graduate students excellent training in a wide range of experimental and theoretical aspects of an inherently interdisciplinary field. Postdoctoral researchers will receive professional mentoring. Commitment to teaching and outreach includes ongoing active undergraduate student involvement in research, as well as contributions to university programs, science fairs, and workshops for domestic and international undergraduates.