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（EEL）是一种极其强大且发达的技术，对于材料物理学研究而变得极为有价值，可提供有关许多低能（0 - 10EV）基本兴奋的光谱信息，例如Valence壳电子兴奋，声音，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，等离子，以及所有波多波多德的电荷密度振荡。还可以测量高能量损失激发（10 - 1000 eV），例如核心电子激发，从而提供类似于X射线抽象光谱的信息，对价值，局部几何形状和吸收物种的结合，这对于基本研究非常重要。但是，常规的鳗鱼只能以同等学位研究材料。在这里，我们建议构建一种新型动量分辨的超快电子能量损失光谱（Q-UEELS）仪器，该仪器与Siwick Lab中现有的超快电子衍射仪无缝集成。该Queels光谱仪在飞行时间的几何形状中利用RF腔，以实现能量和时间的高分辨率，从而提供了能量损失光谱的时间损失光谱，使得飞秒的时间分辨率为picseconds。 Q -ueel提供的新测量能力将有助于发现光诱导的结构变化对材料特性的影响以及材料在其自然尺度上的材料（suba -nm），时间（FS -PS）和能量（MEV -ev）的材料中的光兴奋性动态，仅通过揭示有关先前隐藏的关于以前隐藏的典型兴奋的信息。该提案利用了锡威克组的两个最新进展，代表了一个令人兴奋的新科学机会，以开发鳗鱼研究远离平衡的材料特性。