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Research Focus B

Probing and controlling electrons

In the microcosm the borders between biology, chemistry and physics disappear. The electron's atomic-scale motion is reponsible for the undesirable and the desired radiation-induced damage to biological matter in cancer diagnostics and therapy, respectively, just as for chemical changes of molecular structure and the phenomena of atomic physics. In Research Focus B we will be utilising the most advanced light sources currently available for looking into the electronic structure and dynamics of matter with unprecedented spectral and temporal resolution. Research Focus B "Probing and controlling electrons" capitalises on cutting-edge laser, laser-driven XUV, X-ray and ion sources as well as recent methodological advances in the fields of frequency- and time-resolved metrology.

These sources emerge from the technological developments in Research Focus A (Next-generation sources and device technology), which provide the footing for research into novel biomedical techniques in Research Focus C (Biomedical imaging and radiation therapy with brilliant X-rays and particle beams). Moreover, addressing fundamental questions of radiation biology with the tools and techniques of femto-/ attosecond spectroscopy also directly interlinks Research Focus B and Research Focus C (Biomedical imaging and radiation therapy with brilliant X-rays and particle beams). In Research Focus B we shall investigate intricate electronic and molecular phenomena in well-defined environments to develop an understanding of elementary processes that are of fundamental importance in selected physical, chemical and biomedical applications.

Furthermore, we shall focus on challenging issues regarding the understanding and control of electron dynamics, photostimulated charge transfer and electron emission as well as the foundations of ultrafast lightwave electronics. Experimental work will be inspired and supported by a network of theory groups with complementary expertise spanning over LMU, MPQ and TUM.

Fig. B.1: Position of Research Focus B within MAP

Grand challenges and questions in Research Focus B

1) Can electron correlations in atoms, molecules and the build-up of the band structure of solids be disentangled in real time and controlled by synthesised fields?
We will synthesise light fields at frequencies spanning over the VUV-UV-VIS-IR range and use these, along with synchronised attosecond XUV pulses, for triggering, steering and observing electron dynamics with attosecond time resolution in a wide range of systems including isolated atoms and molecules, molecular assemblies and nano-films on surfaces as well as solids.

2) Can coupled electronic-nuclear dynamics and primary photo-induced dynamics, such as electron / proton transfer, be deciphered in organic / biological molecules?
We will study strongly coupled electronic and vibrational dynamics, energy and charge transfer with few-fs-resolution UV photoelectron spectroscopy, coherent multi-pulse spectroscopy and multidimensional nonlinear frequency-comb spectroscopy. Few-fs UV and attosecond XUV pulses will also capture the formation, motion and decay of electronic wavepackets. Studies performed in gas and liquid phase as well as on molecules assembled on surfaces will reveal the specific influence of the environment on the dynamics and reaction pathways.

3) Can dynamic changes of electronic / nuclear structures of complex molecules and solidstate systems be directly captured with time-resolved X-ray and electron diffraction?
We will use sub-ps / sub-10-fs X-ray pulses from a plasma / undulator source for time-resolved diffraction experiments on organic molecules and biological systems. Diffraction with sub-100-fs (on the long run --> sub-fs) single-electron pulses will reveal electronic charge motion in molecules and nanostructures. The two methods will deliver complementary information of electronic motion and chemical transformations and of ultrafast phase transitions in nanoscale materials.

4) Can the microscopic mechanisms behind particle cancer therapy be understood and can this insight benefit the therapy?
We will expand the new field of ultrafast radiation biology by studying the primary processes following irradiation of biological matter with femtosecond ion beams by using synchronised femtosecond laser and X-ray pulses. This synchronism will be a unique feature of the emerging CALA facility, allowing, for the first time, real-time insight into dynamics within 1 picosecond of the ion impact and hence, fundamental processes underlying particle therapy.

5) How does Ångstrom-scale electron transport occur in solids and at interfaces and how can it be manipulated in nano-patterned materials?
We will apply attosecond streaking metrology on well defined adlayer structures on solids to study electron transport through these systems in real time. We will perform pump / probe experiments with few-fs UV pump and attosecond XUV probe pulses on molecules chemisorbed to surfaces. Comparison will be made to structured materials that are expected to alter functionality.

6) Is light-field control and real-time observation of electronic motion in nanoscaled matter feasible and can electronics be sped up to lightwave (petahertz) frequencies?
We aim at using controlled few-cycle light fields for the control and observation of electron currents in nanostructured surfaces, nanotips and nanofilms with attosecond precision. These investigations will build the basis for the demonstration of switching electric currents in solid-state nano-devices at lightwave frequencies and explore the ultimate speed limits of electronics.