An RF cavity-based ultrafast electron energy loss spectrometer: A new tool for unraveling dynamic processes in materials

基于射频腔的超快电子能量损失谱仪：一种用于揭示材料动态过程的新工具

• 批准号: RTI-2018-00862
• 负责人: Siwick, Bradley
• 金额: $ 10.85万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=642248
• 关键词: RF; cavity; based; ultrafast; electron

Electron energy loss spectroscopy (EELS) is an extremely powerful and well developed technique that has become extremely valuable for materials physics studies, providing spectroscopic information on a number of low energy (0 – 10eV) elementary excitations like valence shell electron excitations, phonons, plasmons and charge density oscillations of all kinds at all wavevectors. High-energy loss excitations (10 – 1000 eV) like core-electron excitations can also be measured, providing information similar to xray absorption spectroscopy on valency, local geometry and bonding of the absorbing species that has been so important for fundamental studies. Conventional EELS, however, is only capable of studying materials at equilibrium. Here we propose to construct a novel momentum-resolved ultrafast electron energy loss spectroscopy (q-uEELS) instrument that seamlessly integrates with the existing ultrafast electron diffractometer in the Siwick lab. This q-uEELS spectrometer makes use of RF cavities in a time-of-flight geometry to enable high resolution in both energy and time, providing energy loss spectra with a time resolution of femtoseconds to picoseconds. The new measurement capabilities provided by q-uEELS will help uncover the effects of photoinduced structural changes on material properties and the dynamics of optical excitation in materials on their natural scales of length (subA - nm), time (fs–ps) and energy (meV - eV) simultaneously by revealing the previously hidden information about characteristic excitations contained in the inelastic electron scattering. This proposal leverages two very recent advances in the Siwick group and represents an exciting new scientific opportunity to develop EELS for studies of material properties far from equilibrium.

电子能量损失光谱 (EELS) 是一种极其强大且成熟的技术，对于材料物理研究来说非常有价值，提供有关许多低能 (0 – 10eV) 基本激发（如价层电子激发、声子、等离子体激元）的光谱信息以及所有波矢量上的各种电荷密度振荡，例如核心电子激发，也可以是高能量损失激发（10 – 1000 eV）。测量，提供类似于X射线吸收光谱的吸收物质的化合价、局部几何形状和键合的信息，这些信息对于基础研究非常重要，但是，它只能研究平衡状态的材料。动量分辨超快电子能量损失光谱 (q-uEELS) 仪器与 Siwick 实验室现有的超快电子衍射仪无缝集成。该 q-uEELS 光谱仪利用 RF。 q-uEELS 提供的新测量功能将有助于揭示光引起的结构变化的影响。通过揭示先前隐藏的有关特征激发的信息，同时研究材料属性和材料中自然尺度的长度（亚纳米 - 纳米）、时间（飞秒 - 皮秒）和能量（毫伏 - eV）的光激发动力学该提案利用了 Siwick 小组的两项最新进展，代表了开发 EELS 以研究远离平衡状态的材料特性的令人兴奋的新科学机会。