In many materials systems, such as catalytic nanoparticles, the ability to characterize dynamic atomic structural changes is important for developing a more fundamental understanding of functionality. Recent developments in direct electron detection now allow image series to be acquired at frame rates on the order of 1000 frames per second in bright-field transmission electron microscopy (BF TEM), which could potentially allow dynamic changes in the atomic structure of individual nanoparticles to be characterized with millisecond temporal resolution in favorable cases. However, extracting such data from TEM image series requires the development of computational methods that can be applied to very large datasets and are robust in the presence of noise and in the non-ideal imaging conditions of some types of environmental TEM experiments. Here, we present a two-dimensional Gaussian fitting algorithm to track the position and intensities of atomic columns in temporally resolved BF TEM image series. We have tested our algorithm on experimental image series of Ce atomic columns near the surface of a ceria (CeO2) nanoparticle with electron beam doses of ~125-5000 e-Å-2 per frame. The accuracy of the algorithm for locating atomic column positions is compared to that of the more traditional centroid fitting technique, and the accuracy of intensity measurements is evaluated as a function of dose per frame. The code developed here, and the methodology used to explore the errors and limitations of the measurements, could be applied more broadly to any temporally resolved TEM image series to track dynamic atomic column motion.

中文翻译：

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在动态结构变化过程中跟踪原子柱的皮尺度空间运动

在许多材料系统中，例如催化纳米粒子，表征动态原子结构变化的能力对于发展对功能的更基本理解非常重要。直接电子检测的最新发展现在允许在明场透射电子显微镜 (BF TEM) 中以每秒 1000 帧的帧速率获取图像系列，这可能允许单个纳米粒子的原子结构发生动态变化在有利的情况下具有毫秒级的时间分辨率。然而，从 TEM 图像系列中提取此类数据需要开发可应用于非常大的数据集的计算方法，并且在存在噪声和某些类型的环境 TEM 实验的非理想成像条件下具有鲁棒性。这里，我们提出了一种二维高斯拟合算法来跟踪时间分辨 BF TEM 图像系列中原子柱的位置和强度。我们已经在靠近二氧化铈 (CeO2) 纳米粒子表面的 Ce 原子柱的实验图像系列上测试了我们的算法，电子束剂量为每帧 ~125-5000 e-Å-2。将用于定位原子列位置的算法的精度与更传统的质心拟合技术的精度进行比较，并且强度测量的精度被评估为每帧剂量的函数。此处开发的代码以及用于探索测量误差和局限性的方法可以更广泛地应用于任何时间分辨 TEM 图像系列，以跟踪动态原子柱运动。