The Emergence of Metallic Properties in Free Metal Clusters in a Molecular Beam

*非技术摘要*人们对纳米物体的性质越来越感兴趣。然而，人们对最小的金属粒子或团簇的性质知之甚少，因为它们只由几个原子组成。有可能生产出这些极小的粒子，并在真空室中研究它们的性质。这一个人研究人员奖支持一个项目，该项目将产生一束小金属团簇，随后将其冷却到极低的温度。然后这些粒子束在电场和磁场中偏转。磁偏转提供了有关团簇磁性的关键信息，可以与块体材料的磁性进行比较。电场中的偏转表明这些微小的金属颗粒是否导电。有一些证据表明，即使在室温下，某些金属团簇也具有类似于超导的性质。这些基础研究将提供关于是什么使金属成为金属的重要信息。它们还将表明特定的金属团簇是否可用于纳米技术应用，如磁记录。研究生和本科生将学习各种实验技术，为他们未来在学术界或工业界的职位做准备。他们接受的培训将为他们提供所需的技能，使他们成为纳米电子物体特性的前沿研究人员。该奖项由材料研究部和物理部资助。*技术摘要*这一个人研究人员奖支持一个项目，该项目解决了金属团簇中金属性质如何作为尺寸函数发展的基本问题。利用脉冲激光蒸发方法在低温团簇光源中产生了原子从1个到数百个的小金属团簇光束，并在高真空中研究了它们的性质，因为它们从源飞行到位置灵敏的质量分析仪，可以同时测量团簇的质量和位置。温度约为20K的团簇基本上处于电子和振动基态，因此非常适合于研究材料的基态性质。大体上，金属不能承受电压差，因此大块金属物体不能有电偶极矩。因此，对小星团的电偶极子测量将提供有关这一重要金属性质出现的信息。分子束电子自旋共振测量顺磁团簇的磁矩将跟踪小的碱团簇和Nb团簇中g值的尺寸演化。在后一种情况下，这些测量可以提供对铁电状态和超导电性之间可能联系的洞察。研究生和本科生将学习各种实验技术，为他们未来在学术界或工业界的职位做准备。接受的培训将为他们提供所需的技能，使他们成为纳米电子物体特性的前沿研究人员。该奖项由材料研究部和物理部资助。

****NON-TECHNICAL ABSTRACT****There is an increasing interest in the properties of nanoscopic objects. Yet little is known about the properties of the very smallest metal particles, or clusters, which consist of only a few atoms. It is possible to produce these extremely small particles and to study their properties in a vacuum chamber. This individual investigator award supports a project that will produce a beam of small metallic clusters, which are subsequently cooled to extremely low temperatures. Beams of these particles are then deflected in electric and magnetic fields. The magnetic deflections provide critical information about the magnetic properties of the clusters, which can be compared with magnetic properties of bulk materials. Deflections in electric fields show whether these small metal particles conduct electricity or not. There is some evidence that certain metal clusters have properties akin to superconductivity even at room temperature. These fundamental studies will provide important information about what makes a metal a metal. They will also indicate whether specific metal clusters may be useful for nanotechnology applications such as magnetic recording. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training they receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics.**** TECHNICAL ABSTRACT****This individual investigator award supports a project that addresses the fundamental question of how metallic properties develop in metallic clusters as a function of size. Beams of small metal clusters with from one to several hundred atoms are produced in a cryogenic cluster source using the pulsed laser vaporization method and their properties are studied in high vacuum as they fly from the source to a position sensitive mass analyzer that can simultaneously measure both the mass and the positions of the clusters. Clusters with temperatures of about 20 K are essentially in their electronic and vibrational ground states and therefore are ideally suited for studying the ground state properties of the material. In the bulk, metals do not tolerate a voltage difference and therefore bulk metal objects cannot have electric dipole moments. Hence electric dipole measurements of small clusters will provide information on the emergence of this important metallic property. Molecular beam electron spin resonance measurements of the magnetic moments of paramagnetic clusters will trace the size evolution of the g-values in small alkali clusters and in niobium clusters. In the latter case these measurements may provide insight into a possible connection between a ferroelectric state and superconductivity. Graduate and undergraduate students will learn a variety of experimental techniques that will prepare them for future positions in academia or industry. The training the receive will provide them with the skills needed to become forefront researchers in the properties of nanoscopic electronic objects. This award receives funding from the Division of Materials Research and the Division of Physics.