Spectroscopy and Dynamics of Semiconductor, Metal, and Carbon Clusters using Photoelectron Imaging

使用光电子成像的半导体、金属和碳团簇的光谱学和动力学

• 批准号: 0505311
• 负责人: Daniel Neumark
• 金额: $ 45万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-15 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0505311&HistoricalAwards=false
• 关键词: Spectroscopy; Dynamics; Semiconductor; Metal; Carbon

This project addresses valence band spectroscopy and electronic relaxation dynamics in semiconductor, metal, and carbon clusters investigated by two methods: anion photoelectron imaging using vacuum ultraviolet (VUV) light sources, and femtosecond time-resolved photoelectron imaging. The VUV experiments will focus on mapping out the valence band structure of size-selected indium phosphode and silicon semiconductor clusters. Photodetachment at high energies, particularly at 10.5 electron-volts, will probe more deeply into the valence bands of these species than has been previously possible. Detection of the ejected photoelectrons using velocity-map imaging (VMI) will provide simultaneous determination of photoelectron kinetic energy and angular distributions, while also discriminating between direct photodetachment and thermionic emission. The time-resolved photoelectron imaging (TRPEI) experiments will track relaxation pathways in electronically excited clusters. TRPEI will be used to follow internal conversion and Auger decay dynamics in mercury clusters. It will also be applied to electronic relaxation dynamics in indium phosphide cluster anions, and in pure and metal-doped fullerides. Success on this project requires a combination of critical and independent thinking along with expertise in a wide range of laboratory instrumentation, including vacuum, lasers, electronics, and computer programming. Students trained in these broad areas are highly competitive in the job market.%%%The proposed research program in cluster science focuses on how the properties of matter, particularly semiconductors and metals, evolve between the molecular and bulk size regimes. As such, it provides a fundamental framework for understanding the foundations of nanoscience and nanotechnology. The increasing emphasis on nanotechnology in basic research and society as a whole has stimulated much interest in fundamental questions of cluster science. While nanoscience focuses on how the properties of bulk materials differ in the nanoscale regime, cluster science has traditionally focused on how the properties of atoms and molecules evolve upon aggregation. This approach, in which one investigates changes in the geometry and spectroscopy of clusters with increasing size, has been extremely productive. However, in recent years, there has been much interest in a parallel question, namely how large does a cluster have to be in order to observe the analog of phenomena normally associated with bulk materials, such as band structure in semiconductors, metal-insulator transitions, electron solvation in liquids, and thermionic emission. The proposed research will address many of these issues. It will also contribute significantly to the scientific infrastructure of the U.S. by providing state-of-the-art research training to young researchers at the undergraduate, graduate, and post-doctoral levels. This NSF project is being co-funded by the Chemistry Division and the Division of Materials Research.

该项目解决了通过两种方法研究的半导体，金属和碳簇中的价带光谱和电子弛豫动力学：使用真空紫外线（VUV）光源进行研究，以及空位时间秒的时间分辨光电发光。 VUV实验将集中于绘制尺寸选择的im磷和硅半导体簇的价带结构。 在高能量（尤其是在10.5个电子伏特时）的光检查将比以前更深入地探测到这些物种的价带中。 使用速度映射成像（VMI）检测弹出光电子将同时确定光电子动能和角度分布，同时还可以区分直接光检查和热电话发射。 时间分辨的光电子成像（TRPEI）实验将跟踪电子激发簇中的松弛途径。 TRPEI将用于遵循汞簇中的内部转换和螺旋衰减动力学。 它也将应用于磷化磷化物簇阴离子的电子弛豫动力学，以及纯和金属掺杂的富勒底层中。 该项目的成功需要将批判性和独立思考以及在各种实验室仪器中的专业知识（包括真空，激光，电子设备和计算机编程）结合使用。 在这些广泛领域接受培训的学生在就业市场上具有很高的竞争力。%%％集群科学的研究计划重点介绍物质（尤其是半导体和金属的物质）如何在分子和散装尺寸制度之间发展。因此，它为理解纳米科学和纳米技术的基础提供了一个基本框架。 对基础研究和整个社会中纳米技术的越来越重视引起了人们对集群科学的基本问题的极大兴趣。 尽管纳米科学侧重于纳米级政权的大量材料的性质如何不同，但群集科学传统上专注于原子和分子的特性如何在聚集中进化。 这种方法在其中研究了大小增加的群集的几何形状和光谱法的变化，这是极其富有成效的。 然而，近年来，人们对一个平行的问题引起了极大的兴趣，即要观察通常与散装材料相关的现象的类似物，例如半导体，金属绝缘体跃迁，液体中的电子溶解度和热量发射。 拟议的研究将解决许多此类问题。 这也将通过向本科，研究生和博士后水平的年轻研究人员提供最先进的研究培训来为美国的科学基础设施做出重大贡献。 该NSF项目由化学部和材料研究部共同资助。