Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 22: Poster Surface Reactions

O 22.6: Poster

Monday, March 17, 2025, 18:00–20:00, P2

Characterization of an unexpected mu3 adsorption of molecular oxygen on Ag(100) with LT-STM — •Merve Ercelik¹, Andrés Pinar Solé¹, Liang Zhang², Hua Guo², Andreas J. Heinrich¹, Yujeong Bae¹, and Dmitriy Borodin¹ — ¹Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, South Korea — ²Department of Chemistry and Chemical Biology, Center for Computational Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA

The interaction between molecular oxygen and metal surfaces is a key topic in quantum chemistry and surface science, with significant implications for electrochemistry and heterogenous catalysis. Using low-temperature scanning tunneling microscopy (STM), we investigate a previously unknown adsorption state of molecular oxygen on Ag(100), where the molecule binds to three silver atoms simultaneously (mu3-O2). We characterize vibrational excitations through inelastic electron tunneling spectroscopy (IETS): out-of-plane hindered rotation, in-plane hindered rotation, and in-plane hindered translation. Tunneling electron induced rotations reveal a rotational isomerization barrier of 69.3 meV. Interestingly, GGA-level DFT calculations fail to identify mu3-O2 as a stable adsorption state, likely due to self-interaction errors affecting the description of localized charges. We speculate that the mu3-O2 configuration corresponds to a formal molecular oxygen anion, with the 11 meV excitation observed in IETS attributed to a transition between spin-orbit states of the surface-bound molecular anion.

Keywords: Oxygen; Action Spectroscopy; Inelastic Tunneling Spectroscopy; Adsorption; STM