Time resolved resonant x-ray emission spectroscopy

Time-resolved valence-to-core X-ray emission spectroscopy (tr-RXES) is a powerful and versatile technique that enables the investigation of transient electronic structures and their dynamics in various materials, such as solids, solutions, and membranes.  This method provides insights into the occupied electronic states and ligand environment surrounding a metal of interest, enabling the study of orbital splittings, spin-, and oxidation-states.
In comparison, tr-XAS focuses on the unoccupied electronic levels and is more sensitive to the local symmetry and coordination.
In tr-RXES, a sample is excited by a pump pulse (usually a laser), followed by a time-delayed probe pulse consisting of monochromatic X-rays tuned to an appropriate absorption edge. The emitted X-rays are then collected and analyzed, revealing the valence-to-core transitions occurring within the system. These transitions involve the valence electrons of the ligands and provide crucial information about the ligand environment, orbital splittings, and spin- and oxidation-states of the metal center. Additionally, the technique is sensitive to low-energy excitations arising from local, nearest-neighbor, and collective interactions.

One of the main advantages of tr-RXES is its time-resolved capability, which allows for the study of ultrafast processes, such as the formation and decay of reactive intermediates in photoreactions. By varying the time delay between the pump and probe pulses, it is possible to capture transient phenomena occurring on femtosecond to picosecond timescales, providing a detailed picture of the dynamic processes taking place within the sample.
In summary, time-resolved valence-to-core X-ray emission spectroscopy is a cutting-edge technique that offers a unique perspective on the electronic structure and dynamics of various materials. Its ability to probe the ligand environment, capture ultrafast processes, and provide complementary information to other X-ray spectroscopic techniques makes it an invaluable tool for researchers aiming to unravel the intricate processes governing the behavior of matter at the atomic and molecular level.

The pumped (red dotted curve) and unpumped (black dotted curve) RXES spectra at positive (+200 fs) and negative time delays (−100 fs) taken at the carbon K edge (incident photon energy hν = 295 eV) of an HOPG sample are shown. The normalized intensity of the RXES spectra is plotted vs the photon energy loss.

Last Updated on Thursday, 04 May 2023 09:27