Periodic Reporting for period 4 - COCONIS (Coherent multidimensional spectroscopy of controlled isolated systems)
Periodo di rendicontazione: 2021-03-01 al 2022-02-28
The completed setup for 2-dimensional spectroscopy was first tested on atomic samples in a gas cell, before successfully performing the worldwide first experiments on a doped helium nanodroplet beam at millikelvin temperatures. The application of multidimensional spectroscopy to the well-controlled sample revealed many high-resolution details and allowed us to deduce a conclusive picture of the coherent and incoherent ultrafast dynamics of the system. With this experimental demonstration, we achieved a major milestone in our ERC project and a long-standing goal in coherent multidimensional spectroscopy.
Furthermore, new data acquisition schemes and detection types in nonlinear spectroscopy have been developed. We have built a unique experimental apparatus, facilitating 2D spectroscopy measurements with three different types of detection: photoelectron and ion-mass spectrometry as well as fluorescence detection. We established a specialized undersampling technique which permits high lock-in data recovery performance even at very low signal rates, and also engineered an advanced digital signal processing scheme including software-based multichannel lock-in detection to facilitate real-time analysis of data. Finally, we extended the method of phase-modulated nonlinear spectroscopy into the extreme ultraviolet spectral range, using the free-electron laser FERMI as light source. As demonstration example, we probed for the first time the electronic dephasing of a core-shell transition in real time.
The first experiments on the manipulation of XUV femtosecond pulses from the free-electron laser FERMI have demonstrated the possibility of coherent spectroscopy at XUV or even X-ray light sources without the direct manipulation of XUV/X-ray light pulses. Experiments are expected even using XUV table-top HHG laser sources for coherent spectroscopy with a time resolution in the attosecond range. This would open new perspectives for the numerous scientific groups operating these kind of light sources in their laboratories. In the XUV energy range, unprecedented spatial resolution can be gained by addressing inner-shell resonances of individual atoms in a molecular compound and attosecond time resolution can be achieved with ultrashort attosecond pulse generation.
Replacing the complex and costly lock-in hardware needed for the acquisition and analysis of phase-modulated data by digital data processing and specific algorithms is a further goal of the project. We are already at the stage, successfully testing systems in a post-processing fashion. A digital online processing of the experimental data seems to be feasible and is expected to be realized.