kMap.py: A Python program for simulation and data analysis in photoemission tomography

arXiv (Cornell University)

Abstract

For organic molecules adsorbed as well-oriented ultra-thin films on metallic surfaces, angle-resolved photoemission spectroscopy 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 gains 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 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 adsorbate layers, we expect kMap.py to serve as an ideal analysis software to further extend the applicability of PT.

Authors 5

1. Dominik Brandstetter

   University of Graz · Nawi Graz

   Affiliation as printed

   Karl-Franzens-Universität Graz, Institut für Physik, NAWI Graz, 8010 Graz, Austria

2. Xiaosheng Yang Aachen Experimentalphysik IV A

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance · University of Graz · Nawi Graz

   Affiliation as printed

   Experimentalphysik IV A, RWTH Aachen University, 52074 Aachen, Germany

   Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany

   Karl-Franzens-Universität Graz, Institut für Physik, NAWI Graz, 8010 Graz, Austria

   Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany

3. Daniel Lüftner

   University of Graz · Nawi Graz

   Affiliation as printed

   Karl-Franzens-Universität Graz, Institut für Physik, NAWI Graz, 8010 Graz, Austria

4. Frank Stefan Tautz Aachen Experimentalphysik IV A

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Experimentalphysik IV A, RWTH Aachen University, 52074 Aachen, Germany

   Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany

   Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany

5. Peter Puschnig corresponding

   University of Graz · Nawi Graz

   Affiliation as printed

   Karl-Franzens-Universität Graz, Institut für Physik, NAWI Graz, 8010 Graz, Austria