Abstract：
The concept of electronic orbitals has enabled the understanding of a wide range of physical and chemical properties of solids through the definition of, for example, chemical bonding between atoms. In the transmission electron microscope, which is one of the most used and powerful analytical tools for high-spatial-resolution analysis of solids, the accessible quantity is the local distribution of electronic states. However, the interpretation of electronic state maps at atomic resolution in terms of electronic orbitals is far from obvious, not always possible, and often remains a major hurdle preventing a better understanding of the properties of the system of interest. In this review, the current state of the art of the experimental aspects for electronic state mapping and its interpretation as electronic orbitals is presented, considering approaches that rely on elastic and inelastic scattering, in real and reciprocal spaces. This work goes beyond resolving spectral variations between adjacent atomic columns, as it aims at providing deeper information about, for example, the spatial or momentum distributions of the states involved. The advantages and disadvantages of existing experimental approaches are discussed, while the challenges to overcome and future perspectives are explored in an effort to establish the current state of knowledge in this field. The aims of this review are also to foster the interest of the scientific community and to trigger a global effort to further enhance the current analytical capabilities of transmission electron microscopy for chemical bonding and electronic structure analysis.
摘要：
电子轨道的概念使人们能够理解固体的各种物理和化学性质,例如,原子间的化学键合。在透射电子显微镜中，这是用于固体高空间分辨率分析的最常用和最强大的分析工具之一，可访问数量是电子状态的本地分布。然而,就电子轨道而言，原子分辨率下的电子状态图的解释远非显而易见，并不总是可能的,并且通常仍然是阻止更好地理解感兴趣系统属性的主要障碍。在这次审查中,介绍了电子状态图的实验方面的当前状态及其作为电子轨道的解释，考虑到依赖于弹性和非弹性散射的方法，在真实和互惠的空间中。这项工作超越了解析相邻原子柱之间的光谱变化，因为它旨在提供更深入的信息，例如,所涉及状态的空间或动量分布。讨论了现有实验方法的优缺点，而要克服的挑战和未来的观点进行了探索，以努力建立在这一领域的知识的现状。本次审查的目的还在于促进科学界的兴趣，并引发全球努力，以进一步提高透射电子显微镜在化学键合和电子结构分析方面的当前分析能力。
