Bonn 2025 – scientific programme

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MO: Fachverband Molekülphysik

MO 25: X-ray Spectroscopy

MO 25.2: Talk

Thursday, March 13, 2025, 15:00–15:15, HS XVI

Enhanced Intermolecular Coulombic Decay in thiophene dimers — •Deepthy Maria Mootheril¹, Anna Skitnevskaya², Xueguang Ren³, Thomas Pfeifer¹, and Alexander Dorn¹ — ¹Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany — ²Irkutsk, Russia — ³Xi’an Jiaotong University, Xi’an 710049, China

Inter-atomic/intermolecular Coulombic decay (ICD) is an important electronic relaxation mechanism after inner-valence ionization of atoms or molecules with weakly bound neighbours, which leads to low-energy electron emissions that can contribute to radiation damage in biological matter. In this work, we investigate ICD in thiophene dimers, five-membered aromatic ring containing sulfur, a third-row element, as a heteroatom, induced by electron collisions (68 eV). A comparison of the projectile energy loss spectra with theoretical single ionization spectra reveals that the ICD process originates from the C 2s⁻¹ inner-valence vacancy in thiophene dimers, which exhibits significant sulfur contributions. Notably, we observe that relaxation of states between the ICD and Auger thresholds results in a strong enhancement of ICD electrons below 4 eV, in contrast to other aromatic ring systems containing second-row atoms. Based on this ‘ICD-only’ decay contribution, we estimate a reduced relative ICD probability above the Auger threshold, where competing Auger channels become significant.

Keywords: Intermolecular Coulombic Decay; Biorelevant molecular clusters; Electron collisions