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.

该项目致力于通过两种方法研究半导体、金属和碳团簇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。 真空紫外实验的重点将是绘制出大小选择的磷化铟和硅半导体团簇的价带结构。 在高能量下，特别是在10.5电子伏特下的光剥离，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提供光电子动能和角分布的同时测定，同时还区分直接光剥离和电子发射。 时间分辨光电子成像（TRPEI）实验将跟踪电子激发团簇的弛豫路径。 TRPEI将用于跟踪汞团簇的内部转换和俄歇衰变动力学。 它也将被应用到磷化铟簇阴离子的电子弛豫动力学，并在纯和金属掺杂的富勒烯。 这个项目的成功需要批判性和独立思考的结合沿着在广泛的实验室仪器，包括真空，激光，电子和计算机编程的专业知识。 在这些广泛领域接受培训的学生在就业市场上具有很强的竞争力。%%%在集群科学的拟议研究计划的重点是如何物质，特别是半导体和金属的性质，分子和散装尺寸制度之间的演变。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。 随着纳米技术在基础研究和整个社会中的日益重视，人们对团簇科学的基本问题产生了浓厚的兴趣。 虽然纳米科学的重点是如何在纳米级制度的散装材料的性质不同，集群科学传统上集中在原子和分子的性质如何演变聚集。 这种方法，其中一个调查的变化，在几何形状和光谱的集群与增加的大小，一直是非常富有成效的。 然而，近年来，人们对一个平行的问题很感兴趣，即一个团簇必须有多大才能观察到通常与块状材料相关的现象，如半导体中的能带结构，金属-绝缘体转变，液体中的电子溶剂化和电子发射。 拟议的研究将解决其中许多问题。 它还将通过为本科生，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，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。