液-汽界面处具有化学特异性的埃级深度分辨
Ångstrom depth resolution with chemical specificity at the liquid-vapor interface
AI总结：
本文提出利用芯能级光电子角分布的各向异性参数与原子沿表面法线平均距离的线性关系，在液-汽界面实现约1 Å的化学特异性深度分辨。
摘要：
界面深度分布的测定在许多科学和技术领域中具有首要重要性。光电子能谱原则上非常适合这一目的，然而由于缺乏对液体中电子散射过程的理解，针对液-汽界面的定量实现受到阻碍。先前的研究表明，芯能级光电子角分布（PADs）会因深度相关的弹性电子散射而改变，因此可以揭示物种在界面上的深度分布信息。在此，我们进一步探索这一概念，并表明表征PAD的各向异性参数随原子沿表面法线方向的平均距离线性变化。这种行为可以在低碰撞数区域中得到解释。我们还表明，不同原子物种的结果可以在同一长度尺度上进行比较。我们证明，沿表面法线方向相隔约1 Å的原子可以通过该方法被清晰地区分，从而实现优异的深度分辨率。
英文摘要：
The determination of depth profiles across interfaces is of primary importance in many scientific and technological areas. Photoemission spectroscopy is in principle well suited for this purpose, yet a quantitative implementation for investigations of liquid-vapor interfaces is hindered by the lack of understanding of electron-scattering processes in liquids. Previous studies have shown, however, that core-level photoelectron angular distributions (PADs) are altered by depth-dependent elastic electron scattering and can, thus, reveal information on the depth distribution of species across the interface. Here, we explore this concept further and show that the anisotropy parameter characterizing the PAD scales linearly with the average distance of atoms along the surface normal. This behavior can be accounted for in the low-collision-number regime. We also show that results for different atomic species can be compared on the same length scale. We demonstrate that atoms separated by about 1~Å~along the surface normal can be clearly distinguished with this method, achieving excellent depth resolution.
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