Timely topics of atomic and molecular physics with femtosecond x-ray free-electron laser sources
Abstract:
X-ray free-electron laser sources (XFELs) are accelerator based short-pulse, high-intensity x-ray sources that reach an unprecedented parameter regime and have the potential to induce paradigm shifts in science areas ranging from structural biology, plasma physics, solid-state physics, quantum and nonlinear optics, and chemistry. With pulse durations in the femtosecond time domain, i.e the time-scale at which chemical bonds break and form, XFELs open the pathway to study chemical reaction dynamics in complementary ways to traditional optical-laser based techniques. Moreover, these new sources can reach unrivalled intensity regimes, surpassing typical intensities of the brightest synchrotron radiation sources, by 10-11 orders of magnitude. This opens new opportunities for first studies of nonlinear optical effects in the x-ray region. The lecture series will start with an introduction to the theory of x-ray matter interaction, discussing fundamental processes such as photoionization, resonant excitation, elastic and inelastic x-ray scattering. The physics, working principle and characteristics of x-ray free-electron lasers will be discussed. Subsequently, I will give a broad survey of current activities in atomic and molecular physics at XFEL sources. A focus will be given to introduce different pump-probe techniques, based on photoelectron spectroscopy, Auger spectroscopy, transient absorption techniques, x-ray emission spectroscopy and inelastic x-ray scattering techniques (Raman scattering). These techniques allow to unraveling electronic and nuclear dynamics in small molecular systems. The different techniques will be highlighted by current theoretical and experimental research in that field. An outlook on new nonlinear spectroscopic techniques in the x-ray domain will be given.