Barwick Brett, Park Hyun Soon, Kwon Oh-Hoon, Baskin J Spencer, Zewail Ahmed H
Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2008 Nov 21;322(5905):1227-31. doi: 10.1126/science.1164000.
With advances in spatial resolution reaching the atomic scale, two-dimensional (2D) and 3D imaging in electron microscopy has become an essential methodology in various fields of study. Here, we report 4D imaging, with in situ spatiotemporal resolutions, in ultrafast electron microscopy (UEM). The ability to capture selected-area-image dynamics with pixel resolution and to control the time separation between pulses for temporal cooling of the specimen made possible studies of fleeting structures and morphologies. We demonstrate the potential for applications with two examples, gold and graphite. For gold, after thermally induced stress, we determined the atomic structural expansion, the nonthermal lattice temperature, and the ultrafast transients of warping/bulging. In contrast, in graphite, striking coherent transients of the structure were observed in both image and diffraction, directly measuring, on the nanoscale, the longitudinal resonance period governed by Young's elastic modulus. The success of these studies demonstrates the promise of UEM in real-space imaging of dynamics.
随着空间分辨率提升至原子尺度，电子显微镜中的二维（2D）和三维成像已成为各个研究领域的重要方法。在此，我们报告了超快电子显微镜（UEM）中的四维成像，具有原位时空分辨率。利用像素分辨率捕获选定区域图像动态以及控制脉冲之间的时间间隔以对样品进行时间冷却的能力，使得对转瞬即逝的结构和形态的研究成为可能。我们通过金和石墨这两个例子展示了其应用潜力。对于金，在热致应力作用后，我们确定了原子结构膨胀、非热晶格温度以及翘曲/凸起的超快瞬态。相比之下，在石墨中，在图像和衍射中均观察到显著的结构相干瞬态，直接在纳米尺度上测量了由杨氏弹性模量控制的纵向共振周期。这些研究的成功证明了UEM在动力学实空间成像方面的前景。
