kMappy: A Python program for simulation and data analysis in photoemission tomography
kMappy: A Python program for simulation and data analysis in photoemission tomography
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DOI：
10.1016/j.cpc.2021.107905
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发表时间：
2021-03-05
影响因子：
6.3
通讯作者：
Puschnig, Peter
中科院分区：
文献类型：
--
作者：
Brandstetter, Dominik;Yang, Xiaosheng;Puschnig, Peter
紫外光电子能谱是一种广泛应用于研究表面和界面价电子结构的实验技术。当检测发射电子的强度不仅作为其动能的函数，而且还取决于其发射角时，如在角分辨光电子能谱（ARPES）中所做的那样，可以提取关于所研究样品的电子结构的极其丰富的信息。对于吸附在金属表面上的有机分子，ARPES已经发展成为一种称为光电发射断层扫描（PT）的技术。通过将光发射电子的最终状态近似为自由电子，PT使用光电流的角度依赖性，即所谓的动量图或k图，并将其解释为初始状态分子轨道的傅里叶变换，从而深入了解有机/金属界面的几何和电子结构。在这篇文章中，我们介绍了kMappy，这是一个Python程序，使用户，通过基于PyQt的图形用户界面，模拟分子轨道的光电子动量图，并在模拟和实验之间进行一对一的比较。基于末态的平面波近似，从密度泛函计算中得到的真实的空间分子轨道分布的快速傅里叶变换（FFT），数值计算了模拟的动量图.该程序允许用户改变一些模拟参数，如最终状态动能，分子取向或入射光场的偏振状态。此外，实验光电发射数据也可以加载到程序中，从而实现直接的视觉比较以及自动优化程序，以确定分子的结构参数或分子轨道贡献的重量。随着越来越多的实验组采用光电子能谱成像研究分子吸附层，我们希望kMappy作为一个有用的分析软件，以进一步扩展PT的适用性。(C)2021作者（S）由爱思唯尔公司出版
Ultra-violet photoemission spectroscopy is a widely-used experimental technique to investigate the valence electronic structure of surfaces and interfaces. When detecting the intensity of the emitted electrons not only as a function of their kinetic energy, but also depending on their emission angle, as is done in angle-resolved photoemission spectroscopy (ARPES), extremely rich information about the electronic structure of the investigated sample can be extracted. For organic molecules adsorbed as well-oriented ultra-thin films on metallic surfaces, ARPES has evolved into a technique called photoemission tomography (PT). By approximating the final state of the photoemitted electron as a free electron, PT uses the angular dependence of the photocurrent, a so-called momentum map or k-map, and interprets it as the Fourier transform of the initial state's molecular orbital, thereby gaining insights into the geometric and electronic structure of organic/metal interfaces.In this contribution, we present kMappy which is a Python program that enables the user, via a PyQt-based graphical user interface, to simulate photoemission momentum maps of molecular orbitals and to perform a one-to-one comparison between simulation and experiment. Based on the plane wave approximation for the final state, simulated momentum maps are computed numerically from a fast Fourier transform (FFT) of real space molecular orbital distributions, which are used as program input and taken from density functional calculations. The program allows the user to vary a number of simulation parameters, such as the final state kinetic energy, the molecular orientation or the polarization state of the incident light field. Moreover, also experimental photoemission data can be loaded into the program, enabling a direct visual comparison as well as an automatic optimization procedure to determine structural parameters of the molecules or weights of molecular orbitals contributions. With an increasing number of experimental groups employing photoemission tomography to study molecular adsorbate layers, we expect kMappy to serve as a helpful analysis software to further extend the applicability of PT. (C) 2021 The Author(s). Published by Elsevier B.V.