Posted in | X-Ray Metrology

Chemical State and Electronic Structure with X-Ray Absorption Spectroscopy (XAS) - QuantumLeap-XAS

The QuantumLeap is the first laboratory X-ray absorption spectroscometer (XAS) offering synchrotron-like performance to provide critical information on oxidation states, bond lengths and interatomic distances, electron symmetry, and more.

Research applications include:

  • Catalysts: chemical states of oxides, nitrides, and carbides, size of clusters
  • Nanoparticles characterization: structure and composition
  • Fuel cells, batteries and solar cells: oxidation state of transition metals (e.g., in lithium-ion batteries) as a function of charge and discharge cycles

What is XAS?

X-ray absorption spectroscopy is a technique in which the transmission of x-rays is measured as a function of increasing x-ray energy gradually at energies near the absorption edge (binding energy) of an element of interest, for example: 8.98 keV for copper (K shell).

These calculations give crucial insight on chemical states, such as oxidation states, and also electronic structure, such as bond lengths and electron geometry surrounding the atom.

The two regimes of XAS: XANES (structures nearest to the edge) and EXAFS (typically includes structures around 1 keV above the absorption edge)

The two regimes of XAS: XANES (structures nearest to the edge) and EXAFS (typically includes structures around 1 keV above the absorption edge)

XAS is made up of two regimes:

  1. XANES: X-ray absorption near edge structure region: Comprising x-ray energies closest to the absorption edge, this region shows information related to local atomic state (such as chemical state).
  2. EXAFS: Features that emerge after the XANES region and up to 1000 eV or greater than the absorption edge are extended fine structure. The information in this region can be employed to infer neighboring atom information, including chemical coordination environments and bond lengths.

QuantumLeap Capabilities

Sigray’s QuantumLeap system is the first laboratory XAS system with synchrotron-like performance. The system is capable of wide energy (2.1 - 12 keV) XANES and EXAFS measurements within minutes, and is capable of micro-XANES of down to sub 100 um resolution.

Capabilities include:

  • XANES with excellent sub-eV energy resolution
  • High throughput EXAFS for measurements in seconds to minutes
  • Wide energy coverage range: 2.1-12 keV
  • MicroXANES at 100 µm

The synchrotron-like performance is enabled by Sigray’s key patented innovations in XAS acquisition approach, new high efficiency x-rays optics, and its high brightness multi-target x-ray source.

Example of Results

A display of the system’s powerful capabilities is shown below for Fe chemical state analysis, with acquisitions performed at sub-eV energy resolution. Results match synchrotron performance.

Another example is shown below of an aged and unaged fuel cell battery. Such analysis can be used to quickly fingerprint chemical states that indicate degradation.

 

 

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