Coherent Nonlinear Spectroscopy in the XUV Regime (CHOISE)
Developing novel spectroscopy and pulse shaping schemes in the XUV and attosecond regime
The recent development of coherent light sources in the extreme ultraviolet (XUV) and X-ray spectral domain unfolds exciting opportunities for both the spectroscopic study of quantum systems as well as for the control of their static and dynamic properties. In contrast to the light sources available in the visible and infrared domain, the XUV and X-ray regime provides access to extremely short light pulses down to the attosecond range and offers high photon energies. The latter enables addressing inner-shell electrons that serve as highly localized probes of the electron density in molecules or bulk systems. Hence, spectroscopy and control schemes with unprecedented time resolution and spatial selectivity could be developed. This sets the motivation for our research project which has the focus on the development of novel nonlinear spectroscopy and coherent control schemes in the XUV spectral domain.
On the one hand, we develop highly-stable and very sensitive Fourier transform spectroscopy for XUV light sources, both for free-electron lasers (FELs)[1-3] and for tabletop high harmonic generation (HHG)[4]. This serves as basic building-block for advanced nonlinear spectroscopy with high temporal and at the same time high spectral resolution. Our experiments focus on the study of coherent wave packet dynamics, attosecond metrology and two-dimensional spectroscopy of fundamental systems such as atoms, atomic clusters and small molecules. On the other hand, we explore means for pulse shaping and coherent control in the XUV spectral domain[4]. This is interesting from a fundamental perspective to study and control quantum dynamics under extreme conditions. But also in view of making spectroscopy schemes more efficient by suppressing ionization loss channels that are a general problem when working in the XUV and X-ray domain.
Figure 1: Tracking the electronic coherence of an inner-subshell-valence superposition with XUV wave packet interferomtery [1]. a) Excitation scheme in argon atoms. b) Observed attosecond electronic coherences. c) Measurements were performed at the Free Electron Laser facility FERMI in Trieste, Italy.
