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@ARTICLE{Brandstetter:894071,
      author       = {Brandstetter, Dominik and Yang, Xiaosheng and Lüftner,
                      Daniel and Tautz, F. Stefan and Puschnig, Peter},
      title        = {k{M}ap.py: {A} {P}ython program for simulation and data
                      analysis in photoemission tomography},
      journal      = {Computer physics communications},
      volume       = {263},
      issn         = {0010-4655},
      address      = {Amsterdam},
      publisher    = {North Holland Publ. Co.},
      reportid     = {FZJ-2021-03021},
      pages        = {107905 -},
      year         = {2021},
      abstract     = {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-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 kMap.py 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 kMap.py to serve as a helpful
                      analysis software to further extend the applicability of
                      PT.Program summaryProgram Title: kMap.pyCPC Library link to
                      program files:
                      https://doi.org/10.17632/tnrm9jcccc.1Developer’s
                      respository link: https://github.com/brands-d/kMap/Code
                      Ocean capsule:
                      https://codeocean.com/capsule/5788845Licensing provisions:
                      GPLv3Programming language: Python 3.xNature of problem:
                      Photoemission tomography (PT) has evolved as a powerful
                      experimental method to investigate the electronic and
                      geometric structure of organic molecular films [1]. It is
                      based on valence band angle-resolved photoemission
                      spectroscopy and seeks an interpretation of the angular
                      dependence of the photocurrent, a so-called momentum map,
                      from a given initial state in terms of the spatial structure
                      of molecular orbitals. For this purpose, PT heavily relies
                      on a simulation platform which is capable of efficiently
                      predicting momentum maps for a variety of organic molecules,
                      which allows for a convenient way of treating the effect of
                      molecular orientations, and which also accounts for other
                      experimental parameters such as the geometrical setup and
                      nature of the incident photon source. Thereby, PT has been
                      used to determine molecular geometries, gain insight into
                      the nature of the surface chemistry, unambiguously determine
                      the orbital energy ordering in molecular homo- and
                      heterostructures and even reconstruct the orbitals of
                      adsorbed molecules [1–4].Solution method: kMap.py 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 [2] which are used as program input and which
                      are usually obtained from density functional calculations.
                      The user can 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 minimize the
                      difference between simulated and measured momentum maps.
                      Thereby, structural parameters of the molecules [2] and the
                      weights of molecular orbitals to experimentally observed
                      emission features can be determined [3].},
      cin          = {PGI-3},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-3-20110106},
      pnm          = {5213 - Quantum Nanoscience (POF4-521)},
      pid          = {G:(DE-HGF)POF4-5213},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000642455800003},
      doi          = {10.1016/j.cpc.2021.107905},
      url          = {https://juser.fz-juelich.de/record/894071},
}