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O: Fachverband Oberflächenphysik
O 55: Poster Wednesday: Organic Molecules at Surfaces 2
O 55.10: Poster
Mittwoch, 7. September 2022, 18:00–20:00, P4
Surface Chemical Bond of Alternant vs. Non-Alternant Aromatic Isomers — •Florian Münster1, Lukas Ruppenthal1, Leonard Neuhaus1, Jan Herritsch1, Jon Henrick Both1, Pengcai Liu2, Xing-Yu Chen2, Jiawen Cao2, Xiao-Ye Wang2, and J. Michael Gottfried1 — 1Fachbereich Chemie, Philipps-Universität Marburg, Germany — 2College of Chemistry, Nankai University, Tianjin, China
The different effects of the topology of pyrene and cyclohepta[fg]acenaphthylene (acepleiadylene) on the occupied and the unoccupied electronic states as well as on the desorption process from the Cu(111) surface are studied using PES, NEXAFS and TPD. Both molecules are aromatic but differ in their topology. While pyrene has an alternating structure, its constitutional isomer acepleiadylene has a non-alternating one. With TPD, we showed that the desorption of acepleiadylene begins at about 340 K, 40 K higher than for pyrene, indicating a stronger bond to the Cu(111) surface. Using the modified leading edge analysis we find a desorption energy of 152 kJ/mol for acepleiadylene compared to 108 kJ/mol for pyrene, each at monolayer coverage. Furthermore, combining PES and NEXAFS, we were able to assess the energy needed in the excitation process of electrons originating from occupied valance orbitals into unoccupied ones. Here we find a 0.5 eV smaller energy difference for the non-alternating species in comparison to the alternating species.