Probing the Electronic Structure and Chemical Bonding of Cryogenically-Cooled Boron and Metal-Boride Nanoclusters

在化学系化学结构、动力学和机理A （CSDM-A）项目的支持下，布朗大学王来生教授和他的研究小组将利用高分辨率光电子成像和光电子能谱研究尺寸选择的硼和金属硼化物纳米团簇。硼只有3个价电子，而碳有4个，因此硼被认为是缺电子的。硼的电子缺乏导致含硼分子结构复杂，化学键独特，这是研究硼分子的一个挑战。王教授和他的学生将使用自制的激光汽化团簇源生成硼和金属硼化物纳米团簇，并利用光电子能谱和成像结合理论计算来深入了解它们的稳定性、结构和化学键。他们的研究可能会导致新的硼基和硼基纳米结构的发现，并提供有关硼化学和化学键的基础知识。本课题的研究将融入物理化学的教学中，为本科生和研究生提供先进实验仪器设计与建设、计算化学等方面的训练机会。本项目重点研究硼团簇的结构和键合，为深入了解金属-硼键的性质和大型硼团簇的结构演变提供依据，为新型硼基纳米材料的研究奠定基础。为了实现这些研究目标，王来生教授和他的学生们建造了两种不同类型的光电子能谱仪。一种装置包括一个磁瓶光电子分析仪，旨在提供具有大范围光子能量的光电子能谱。分辨率高的光电子能谱提供了电子指纹，这对于与理论计算进行比较来阐明尺寸选择的硼纳米团簇的结构和键合至关重要。第二个装置涉及高分辨率光电子成像，其目的是获得振动信息。开发了一种低温冷却离子阱，从激光汽化源产生冷硼团簇；这是获得硼和金属硼化物团簇的振动分辨光电子能谱所必需的。这个项目更广泛的影响包括发现新的硼基纳米材料，这些材料有可能成为纳米技术的新平台。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Professor Lai-Sheng Wang and his research group at Brown University will investigate size-selected boron and metal-boride nanoclusters using high-resolution photoelectron imaging and photoelectron spectroscopy. Boron has only three valence electrons compared to four in carbon and is thus considered to be electron deficient. The electron deficiency of boron results in complicated structures and unique chemical bonds in boron-containing molecules, which are challenging to investigate. Professor Wang and his students will generate boron and metal-boride nanoclusters using a home-built laser-vaporization cluster source and utilize photoelectron spectroscopy and imaging in conjunction with theoretical calculations to provide insights into their stabilities, structures, and chemical bonding. Their studies could lead to the discovery of novel boron- and boride-based nanostructures, as well as provide fundamental knowledge about boron chemistry and chemical bonding. The research in this project will be integrated into the teaching of physical chemistry, and will provide training opportunities for undergraduate and graduate students in the design and construction of advanced experimental instrumentation and computational chemistry. This project focuses on the structure and bonding of boron clusters to provide insight into the nature of the metal-boron bonds and structural evolution of large boron clusters to lay the foundation for new boron-based nanomaterials. To achieve these research goals, Professor Lai-Sheng Wang and his students have built two different types of apparatus for photoelectron spectroscopy. One apparatus involves a magnetic-bottle photoelectron analyzer and is aimed at providing photoelectron spectra with a wide range of photon energies. Well-resolved photoelectron spectra provide electronic fingerprints, which are crucial for comparison with theoretical calculations to elucidate the structures and bonding of size-selected boron nanoclusters. The second apparatus involves high-resolution photoelectron imaging, which is aimed at obtaining vibrational information. A cryogenically cooled ion trap is being developed to create cold boron clusters from the laser-vaporization source; this is needed to obtain vibrationally resolved photoelectron spectra for boron and metal-boride clusters. The broader impact of this project includes the discovery of novel boron-based nanomaterials with potential as new platforms for nanotechnology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.