My watch list
my.chemeurope.com  
Login  

Looking at molecules from two sides with table-top femtosecond soft-X-rays

03-Jan-2019

MBI Berlin

Fig. 1: Liquid flatjet (solvated urea) illuminated by a broadband soft X-ray pulse obtained by high-order harmonic generation. The insets show the steady-state absorption of Urea at the C and N K-edges extracted from the measurements.

X-ray spectroscopy provides direct access into the nature of chemical bonds, from which the outcome of chemical reactions can be understood. For this, intense activities both at x-ray source development and implementation of new measurement methods is pursued by key research labs. Researchers at the MBI have now successfully combined a table-top laser-based extreme high-order harmonic source for short-pulse soft-x-ray absorption spectroscopy in the water window with novel flatjet technology. They are the first to demonstrate the simultaneous probing of carbon and nitrogen atoms in organic molecules in aqueous solution.

X-ray absorption spectroscopy (XAS) monitors unoccupied electronic orbitals with element specificity, from which the electronic structure can be derived. For the majority of organic molecules the soft-X-ray spectral region (100-1000 eV) is relevant, as K-edge transitions of low-Z elements (C, N, and O), and the L-edges of 3d metals are found there. XAS is typically performed at large scale facilities, such as storage rings or free-electron lasers. Table-top laser-based sources have until now only been sparsely used to probe pure materials, e.g., metals and organic films. So far, measurements of the carbon or nitrogen K-edges of organic molecules in dilute aqueous solution have not been reported.

The research team at the MBI has now developed a bright source of femtosecond soft X-ray pulses, making use of the extreme high-order harmonic generation process. Long-wavelength (1.8 µm) driver pulses generated with an amplified Ti:sapphire laser system were used to generate high-order harmonics well above the conventional spectral range, i.e., now extending up to 450 eV. They have combined this source with liquid flatjet technology fully functioning under vacuum conditions. Steady-state absorption spectra of organic molecules and inorganic salts in a thin (~ 1 µm) sheet of aqueous solution can now be measured, throughout the so-called water window region between 200-540 eV (see Fig. 1). In particular, this technique enables the simultaneous local probing at both carbon and nitrogen sites within the molecules. With this the research team demonstrates the feasibility of following multiple sites within molecular systems, with the potential of probing possible correlations between these sites upon molecular rearrangements.

This investigation represents a major step towards the systematic investigation of ultrafast rearrangements of solution phase molecular systems with femtosecond soft X-ray spectroscopy. New insights into ultrafast charge transport processes and photo-induced reactions in chemistry and biology are envisaged to become accessible.

Facts, background information, dossiers
  • x-ray spectroscopy
  • x-ray absorption sp…
  • nitrogen
More about MBI
  • News

    How molecules teeter in a laser field

    When molecules interact with the oscillating field of a laser, an instantaneous, time-dependent dipole is induced. This very general effect underlies diverse physical phenomena such as optical tweezers, for which Arthur Ashkin received the Nobel Prize in Physics in 2018, as well as the spat ... more

    Electric polarization in the macroscopic world and electrons moving at atomic scales

    Femtosecond x-ray experiments in combination with a new theoretical approach establish a direct connection between electric properties in the macroscopic world and electron motions on the time and length scale of atoms. The results open a new route for understanding and tailoring the proper ... more

    Concepts for new switchable plasmonic nanodivices

    Plasmonic waveguides open the possibility to develop dramatically miniaturized optical devices and provide a promising route towards the next-generation of integrated nanophotonic circuits for information processing, optical computing and others. Key elements of nanophotonic circuits are sw ... more

More about Forschungsverbund Berlin
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE