ATTOSECOND ELECTRON DYNAMICS IN ISOLATED ORGANIC MOLECULES USING CORE-HOLE CLOCK SPECTROSCOPY – ATTOMEMUCHO

The radiation induced damage of a single deoxyribonucleic acid (DNA) molecule in a living cell can occur either through the direct absorption of X-ray radiation in the DNA molecule itself, leading to creation of holes in the atomic core shells and electrons, or indirectly, through ionization of the bulk water within the cell in which the DNA is located. In this case the DNA damage is caused by the OH radicals and electrons formed through a cascade of reactions and secondary ionization processes.

One of the approaches for damage recognition and repair mechanism relies on the conductive properties of DNA. In addition to the widely accepted mechanism of charge transport through the DNA base stacks, it has been recently demonstrated that electron transport can also occur through a periodic DNA backbone. To date, the role of the interplay between the mechanisms of electron transport in DNA through the base stacks and through a periodic backbone remains unknown.

The phenomenon of electron delocalization in periodic structures is also of great relevance in optoelectronics, where charge transport in organic polymers is the key issue for the efficiency of organic photovoltaic devices (solar cells). In conjugated polymers the electric conduction is formed by the ??-electrons delocalized over several carbon atoms along the polymer backbones as well as through inter-chain interactions. However, the role of polymer chain ordering in oriented films for the electron transport remains largely unexplored.

The proposed project addresses the problem of electron dynamics in organic molecules – a topic of great fundamental importance lying at the interface of physics, chemistry and biology. Despite the diversity of applications – from the radiation induced damage in biomolecules to the efficiency of polymer organic solar cells – the global problem boils down to the common scientific objective of developing an original multifaceted approach for tracing extremely fast electron delocalization dynamics in complex molecular systems placed in different media.

The objectives of this project add up to the development of a general method for observation and control of electron dynamics in large organic molecules in the energy domain. The ambition of the current project is to explore and push the potential of the core-hole clock spectroscopy towards the measurements of electron delocalization and transfer in organic molecules placed in different media.

The outstanding instrumental performance of the HAXPES spectrometer in combination with the extremely narrow bandwidth of the GALAXIES beamline at SOLEIL synchrotron facility so far has no analogy in the world and provides an unprecedented opportunity to perform high-resolution high-energy electron spectroscopy in the hard x-ray regime for dilute systems, solid samples as well as recently, in liquid micro-jets. Here, we propose a comprehensive work program exploiting the full experimental capacity of the HAXPES station.

The part of the project, related to liquid-phase studies, relies on the recent technological breakthrough in the field of hard X-ray spectroscopy. Another part of the project, related to gas-phase studies of large biomolecules, stimulates a promising instrumental development, which may potentially interest the broader scientific community. The exploratory character of the proposed research program creates challenges both for experimental techniques and for theoretical approaches. The ambitious scientific objectives of this project drive instrumental development as well as the development of more sophisticated computational methods required for the interpretation of complex experimental results. The societal impact of the project lies in its strong potential to push the limits of the knowledge lying at the interface of natural sciences, with possible implications, on the longer term, in health and technology.