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.

该项目通过两种方法研究半导体、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 (VUV) 光源的阴离子光电子成像和飞秒时间分辨光电子成像。 真空紫外实验将重点绘制选定尺寸的磷化铟和硅半导体团簇的价带结构。 高能下的光分离，特别是 10.5 电子伏特的光分离，将比以前更深入地探测这些物质的价带。 使用速度图成像（VMI）检测喷射的光电子将同时确定光电子动能和角分布，同时还区分直接光脱离和热电子发射。 时间分辨光电子成像（TPEI）实验将追踪电子激发团簇中的弛豫路径。 TRPEI 将用于跟踪汞簇中的内部转换和俄歇衰变动力学。 它还将应用于磷化铟簇阴离子以及纯富勒烯和金属掺杂富勒烯的电子弛豫动力学。 该项目的成功需要将批判性和独立思维与各种实验室仪器（包括真空、激光、电子和计算机编程）的专业知识相结合。 在这些广泛领域接受过培训的学生在就业市场上具有很强的竞争力。%%%集群科学中拟议的研究计划重点关注物质（特别是半导体和金属）的特性如何在分子和块尺寸状态之间演变。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。 基础研究和整个社会对纳米技术的日益重视激发了人们对集群科学基本问题的浓厚兴趣。 纳米科学关注的是散装材料的特性在纳米尺度范围内的差异，而集群科学传统上关注的是原子和分子的特性在聚集时如何演变。 这种方法研究了随着尺寸的增加而发生的团簇几何形状和光谱学的变化，这种方法非常有效。 然而，近年来，人们对一个并行问题产生了很大的兴趣，即簇必须有多大才能观察通常与块体材料相关的现象的模拟，例如半导体中的能带结构、金属-绝缘体跃迁、液体中的电子溶剂化和热电子发射。 拟议的研究将解决其中许多问题。 它还将为本科生、研究生和博士后级别的年轻研究人员提供最先进的研究培训，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。