We report on the first measurements of a XANES spectrum of solvated Fe(CO)5 using an ultrafast laser driven plasma x-ray source operating at 2 kilohertz repetition rate. The measured spectrum is compared to theoretical XANES spectra based on DFT structure calculations of the solvated complex. The used x-radiation is generated by irradiating a solid metal target with ultrafast high-intensity laser pulses. The subsequently generated high-density plasma emits x-ray pulses with sub-picosecond temporal resolution and an x-ray spectrum extends to energies far higher than the desired spectral range. Since these spectral components potentially falsify the XANES measurements, they were suppressed by the x-ray optical setup.
Ultrafast high-intensity laser pulses incident upon condensed matter targets can generate high-density plasmas that emit x-ray pulses with sub-picosecond temporal structure, significant spatial coherence, and high brightness at kilohertz repetition rates. Such laser-driven plasma x-ray sources based on solid and liquid metal targets have been developed in our laboratory. Essential performance features are discussed along with a feasibility evaluation for future routine application in chemical research. Laser-driven x-ray sources are usable for ultrafast x-ray diffraction and ultrafast x-ray absorption spectroscopy. X-ray absorption near-edge spectra of solvated transition metal complexes are presented.
Ultrafast molecular dynamics depends on the structure of the solvated molecule before photo-excitation. This solvation structure, in turn, depends on the solute's interaction with the solvent molecules. Furthermore, the solute's vibrational modes and its structure are correlated, solvent dependent, and can be measured by mid-infrared and x-ray absorption spectroscopy. Such measured spectra are presented and correlated with quantum calculations in order to elucidate the solvation environment of various transition metal coordination complexes.
Ultrafast high-intensity laser pulses incident upon condensed matter targets can generate solid-density plasmas that emit x-ray pulses with sub-picosecond temporal structure and significant spatial coherence. Such ultrafast laser-driven plasma x-ray sources based on solid and liquid targets are currently under construction in our laboratory. Performance details at several kilohertz laser pulse repetition rates are discussed. As an application of the temporal structure of laser-generated x-ray pulses, ultrafast x-ray absorption fine structure (UXAFS), currently under development, is discussed. It allows, in principle, to measure the structural dynamics of atoms during a chemical process in solution. An overview over UXAFS is presented and properties of our ultrafast x-ray absorption spectrometer are discussed. First calculations of time dependent UXAFS-spectra for ironpentacarbonyl are presented. Ultrafast molecular dynamics depend on the structure of the solvated molecule at the moment of photo-excitation. This structure depends on the solute's interaction with the solvent. Furthermore, the solute's vibrational modes and structure are correlated, solvent dependent, and can be measured by mid-infrared and x-ray absorption spectroscopy. Such measured spectra are presented and correlated with semi-empirical quantum calculations in order to elucidate the solvation environment of transition metal coordination complexes in various solvents.
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