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講座大師 - 第十八屆 |
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| 何文程 教授 |
加州大學爾灣分校物理系教授
美國國家科學院院士
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講題1：Seeing is Believing: the power of microscopy
眼見為憑:顯微術的威力 |
The ability to see has enabled animals and humans to increase the awareness and understanding of their surroundings. Since humans are endowed with the insatiable curiosity and entrepreneurship, the desire to see increasingly small objects has led to the invention of successive instruments that empower the resolution of the eyes. Each jump in the magnification opens a new window for viewing the microscopic world, enabled by the invention of the magnifying glass, the compound microscope, the field ion microscope (FIM), the transmission electron microscope (TEM), and the scanning tunneling microscope (STM). Since all the matter that we see around us are composed of atoms, the ability to first image individual atoms by the FIM was a significant accomplishment. The invention of the TEM ushered in a powerful tool for materials analysis, including imaging of organic compounds and biological matter in real space that complements structural determination by x-ray diffraction in the momentum space. The most recent invention of the electron microscopes is the STM which is based on the quantum mechanical phenomenon of electron tunneling. In the STM, the electrons have energies < 5 eV and thus are less likely to decompose molecules in the sample compared to electrons in the TEM that have at least a thousand times high energies. In this speech, we will highlight some applications of the STM to capture images of atoms and molecules, to resolve their inner components, to measure different types of molecular excitations, and to visualize a number of basic, yet abstract concepts in quantum mechanics that are currently taught in high school chemistry and physics courses.
視覺向來是人類用來認知和理解周遭環境的重要能力，人類與身俱來的開創精神和好奇心驅使我們不斷地發明和改進各種儀器，去看到肉眼無法解析的微觀世界。
從放大鏡，光學顯微鏡，穿透式電子顯微鏡(TEM)，場離子顯微鏡(FIM)，到掃描穿隧顯微鏡(STM)，每一次技術的革新，都進一步開啟了我們對於微觀世界的新視野。例如場離子顯微鏡的成功，讓人類第一次能夠直接觀察原子，而穿透式電子顯微鏡則是實空間材料分析的重要工具 ，在包含了生物和有機材料在內的廣泛領域和X光繞射等相空間的結構分析技術互補分工。
電子顯微術中，相對年輕的成員則是奠基於電子量子穿隧現像的掃描穿隧顯微鏡，其用來進行觀測的電子能量通常小於五電子伏特，比最低能量的穿透式電子顯微鏡少了千倍，因此有著較不容易破壞觀測樣品的特性。
在本次演講將聚焦在掃描穿隧顯微鏡在原子和分子影像上的一些應用，例如解析分子內部的結構，如何量測不同的分子激發機制，同時提供一些高中物理化學中關於量子力學的基礎抽象概念一個比較直觀而且視覺化的理解。
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影片 Part 1 : https://www.youtube.com/watch?v=8RlFXV-VWoE
影片 Part 2 : https://www.youtube.com/watch?v=_l7hxBe7Ezs
影片 Part 3 : https://www.youtube.com/watch?v=xcVwhl6kMhM
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講題2：Imaging the Nature of the Chemical Bond: a new window for viewing molecular sciences
看見化學鍵:為分子科學開啟另一扇窗 |
Röntgen's x-rays striking his wife's hand in 1985 gave the first photograph below the skin of the human body that previously was invisible to the human eyes. The scaffold of bones defined the hand's structure and function. On a much smaller scale, chemists have drawn ball-and-stick models to represent molecules since the dawn of modern chemistry. The skeletal scaffold conveyed similarly the structure and reactivity of molecules. In 2013, we developed the inelastic tunneling probe (itProbe) based on the scanning tunneling microscope (STM) that imaged the positions of each atom and bond within a single molecule, as well as intermolecular interactions. The itProbe enabled the visualization of a molecule as a skeletal scaffold covered by a cloud of outer electrons, much like the fresh covering the bones. Such a probe can be used to image a wide range of molecules and new understanding into the bonding mechanisms can be discovered to reveal previously unknown chemistry of molecules. The itProbe enables a new window for the visualization of chemistry and strives to remove abstraction in the teaching of chemistry and simultaneously impacts research directions. This speech focuses on the extension of the STM to investigate one of the central dogmas of chemistry that relates the molecular structure to the reactivity. We will describe how these measurements are made and apply the technique to several examples that image the nature of the chemical bond.
1895年，科學家倫琴(Röntgen)用X光幫妻子的左手掌拍了史上第一張X光片，人類從此有了能夠看透肌膚觀察活體內部的技術。
肌膚之下，骨骼決定了手掌的結構和功能，而在原子和分子的尺度，早在近代化學的初期，化學家就用球棒模型來描述分子結構，如同骨骼之於手掌，分子的結構決定了分子的特性。
2013年，在掃描穿隧顯微鏡(scanning tunneling microscope (STM))的基礎上，我們發展出了可以同時觀察到分子內原子位置，鍵結和分子間交互作用的非彈性穿隧探針(inelastic tunneling probe (itProbe))。 如同X光讓我們看到包覆在肌膚下的骨骼，藉由itProbe，我們得以觀察到藏在外層電子雲裡的分子結構。
藉由這種探針取得的分子影像可以提供關於鍵結機制的新資訊，增進我們對於分子化學現象的新理解，期望能夠在開創新的科研方向的同時，藉由直觀的視覺影像為基礎化學教育提供新視野，揭開其抽象生澀的面紗。
本講將聚焦於如何將掃描穿隧顯微鏡的應用拓展到分子結構和反應活性相關的化學核心問題的研究上，同時將介紹實驗量測的過程和幾個分子鍵結影像的實例。
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影片 Part 1 : https://www.youtube.com/watch?v=dM4G3qyF-6Q
影片 Part 2 : https://www.youtube.com/watch?v=bqnL_Cz3okc
影片 Part 3 : https://www.youtube.com/watch?v=BlMWqXY5zqI
影片 Part 4 : https://www.youtube.com/watch?v=QmqDc4cqIcs
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