Soft x-ray time-domain interferometry with attosecond precision: Ultrafast spectroscopy and spectro-microscopy in aqueous solutions

• Applicants: Professor Dr. Detlef Kip; Privatdozent Dr. Tim Laarmann; Dr. Jan Rothhardt
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405054418

For the first time, we will perform table-top nanoscale imaging and charge-migration studies in aqueous solutions in the so-called water window of the x-ray spectrum, which allows to study biological samples in their natural environment. Time-domain interferometry will allow to fully exploit the possibilities of the inherently broadband water-window table-top high-harmonic sources by enabling Fourier-transform spectroscopy with unprecedented precision. Combining this time-domain interferometry with the lensless imaging technique ptychography will enable nanoscale spectro-microscopy, namely measuring the complex transmissivity of biological samples with nanoscale spatial resolution and sub-eV spectral resolution. This will allow novel insights into the interior of µm-sized biological objects with elemental- and chemical contrast. The table-top implementation will facilitate a widespread use in biological research and medical applications e.g. the classification of cancer cells, the identification of bacteria and viruses by their nanoscale morphology for customized medication or the study of the interaction of pathogens with infected cells for the development of new treatment strategies. The amino acid molecule glycine in aqueous solution serves as model system for exploring the possible role of nonlocal relaxation processes in the radiation-induced chemical reactivity at the interface between a protein and the fluctuating water network. Up to now, our understanding of the quantum dynamical details of radiation-induced water chemistry on the molecular scale is still in its infancy. Basically, ionization creates a highly reactive medium of ionic and neutral radical species in the radiolysis of liquid water. High-energy photons drive this chemical reaction, which plays an important role in many research topics, such as corrosion processes in water-cooled nuclear power plants or radiation-induced DNA damage of living organisms. Better knowledge of the quantum effects at work, while a chemical bond is broken in aqueous solution, may support controlling, optimizing, and engineering ionizing radiation to be used in radiotherapy for cancer treatment. Here, the understanding of the interplay between intra- and intermolecular (solute-solvent) dynamics, as well as between electronic and nuclear dynamics induced by ionizing radiation on the quantum level of electrons and ions is of utmost importance. The DFG research proposal addresses fundamental physico-chemical questions such as: How does ultrafast charge and energy redistribution proceed during radical formation and decay in hydrated biomolecules?

• DFG Programme: Research Grants