Laboratory for applied X-ray spectroscopy

Experimental studies of fundamental properties of atoms and molecules

Synchrotron radiation-based X-ray spectroscopic techniques are used to study fundamental properties of isolated atoms and molecules. Our main experimental technique is Resonant Inelastic X-ray Scattering (RIXS). In RIXS experiment the incident energy is tuned to a corresponding absorption edge and the subsequent radiative decay is recorded using the emission spectrometer with energy resolution comparable to the resolution of the beamline monochromator and preferably smaller than the lifetime broadening of the spectral features. Several RIXS/XES experimental campaigns at different synchrotrons have been performed in recent years using our tender x-ray emission spectrometer. We have successfully studied multielectron atomic excitations and also structural and dynamic properties of different molecules.

Important publications:

• Separation of Two-Electron Photoexcited Atomic Processes near the Inner-Shell Threshold
• High-resolution x-ray-emission study of 1s4p and 1s3d two-electron photoexcitations in Kr
• Electronic State Interferences in Resonant X-Ray Emission after K-shell Excitation in HCl
• Dissociation of chloromethanes upon resonant σ* excitation studied by x-ray scattering

Electronic structure and chemical speciation studies of different materials

X-ray spectroscopy is employed in different analytical techniques used to study electronic structure of atoms in complex materials. Our tender x-ray emission spectrometer has been used extensively in electronic structure studies of different solid and also liquid materials. In collaboration with the group for Modern Battery Systems at our National Institute of Chemistry, RIXS spectroscopy has been introduced as a powerful tool used to study electrochemical processes in energy storage materials, especially sulfur-based batteries. In addition, the high-energy resolution X-ray emission spectroscopy (XES) method is also successfully combined with MeV proton beam excitation in order to extend the analytical capabilities of standard PIXE technique towards chemical speciation.

Important publications:

• Fingerprinting Mean Composition of Lithium Polysulfide Standard Solutions by Applying High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy
• Chemical speciation using high energy resolution PIXE spectroscopy in the tender X-ray range
• Mechanistic Study of Magnesium–Sulfur Batteries
• Operando Resonant Inelastic X-ray Scattering: An Appropriate Tool to Characterize Sulfur in Li–S Batteries

Inner-shell ionization induced in ion-atom collisions

Atomic inner-shell ionization studies are performed within our home laboratory using MeV ion beams accelerated with the 2 MV Tandem ion accelerator. High energy resolution detection of ion induced x-ray emission is used to resolve contributions from different inner-shell vacancy configurations produced in the collision. This approach is used to study multiple inner-shell ionization induced in such collisions. High-energy resolution was also used to separate spectral contributions originating from different atomic subshells and determine precisely their ionization cross section ratio as a function of ion impact energy.

Important publications:

• Multiple ionization X-ray satellites of magnesium, aluminum and silicon in alpha particle PIXE
• M shell ionization of Ar induced in near-central collisions with MeV protons
• Characteristic plateau in the L1-subshell ionization cross section of Ag induced by proton collisions

• Redox active organic materials for electrical energy storage
• Electrochemistry mechanisms in organic cathode materials studied by X-ray Raman spectroscopy
• Developing tender X-ray spectroscopy probes to tackle problems in materials science and ultrafast science
• Operando metrology for energy storage materials

• Sulfur valence-to-core X-ray emission spectroscopy study of lithium sulfur batteries
• Characterization of Li–S Batteries Using Laboratory Sulfur X-ray Emission Spectroscopy
• Multiple ionization X-ray satellites of Ti and its binary oxides in alpha particle PIXE
• Fingerprinting Mean Composition of Lithium Polysulfide Standard Solutions by Applying High-Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy
• Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses
• Diagram, valence‐to‐core, and hypersatellite Kβ X‐ray transitions in metallic chromium
• Inception of electronic damage of matter by photon-driven post-ionization mechanisms
• Effect of Ag Doping on Electronic Structure of Cluster Compounds AgxMo9Se11 (x = 3.4, 3.9)
• Multiple ionization X-ray satellites of magnesium, aluminum and silicon in alpha particle PIXE
• Chemical speciation using high energy resolution PIXE spectroscopy in the tender X-ray range
• Hypersatellite x-ray decay of 3d hollow-K-shell atoms produced by heavy-ion impact