# Enhanced intermolecular coulombic decay due to sulfur heteroatoms in thiophene dimer

## TL;DR

This study shows that sulfur atoms in thiophene dimers enhance the production of low-energy electrons through a process called intermolecular Coulombic decay.

## Contribution

The study demonstrates that sulfur heteroatoms in thiophene dimers enhance ICD electron emission via inner-valence orbitals below the Auger threshold.

## Key findings

- Sulfur-containing inner-valence orbitals initiate ICD in thiophene dimers.
- ICD electron emission is enhanced compared to other aromatic ring dimers.
- Sulfur plays a pivotal role in shaping the ICD electron spectrum.

## Abstract

Intermolecular Coulombic decay (ICD) is an important relaxation process of excited atoms and molecules in an environment, producing low-energy electrons that may contribute to radiation damage. Despite its significance, the mechanisms influencing ICD in molecular complexes remain unclear. Here, we investigate and unambiguously prove the ICD process in thiophene dimer, an aromatic ring with a third-row atom. Using multi-particle momentum coincidence spectroscopy, accompanied by high-level electronic structure calculations, we elucidate that the ICD process is initiated from the sulfur-containing inner-valence orbitals which are energetically below the Auger threshold. This leads to an enhancement in the emission of low-energy ICD electrons compared to other aromatic ring dimers. By utilizing this ‘ICD-only decay’ contribution we quantify ICD probabilities above the Auger threshold. This study reveals the pivotal role of sulfur in shaping the ICD electron spectrum, which can be implied to control the low-energy electron emission in biological systems.

Low-energy electrons from intermolecular Coulombic decay (ICD) relaxation can contribute to radiation damage. Here, using multi-particle momentum coincidence spectroscopy and high-level electronic structure calculations, the authors show that the presence of sulfur in inner-valence orbitals leads to an enhancement in the emission of ICD low-energy electrons in thiophene.