QuantumLeap XAS X-Ray Absorption Spectroscopy – Electronic and Chemical State Determination
The first laboratory XAS offering synchrotron-like performance
X-ray absorption spectroscopy (XAS) is a powerful chemical analysis technique that can determine the chemical composition and chemical structure of the constituent elements e.g. oxidation state, bond length etc. XAS combines two techniques:
- XANES – X-ray Absorption Near Edge Structure
- EXAFS – Extended X-Ray Absorption Fine Structure
XAS is the measurement of the x-ray absorption coefficient µ(E) is a measure of the X-ray intensity as function of the incident and transmitted X-ray intensity.
- Unprecedented ability to analyse electronic (chemical) state of elements
- First lab micro-XANES system, providing spatial resolution down to 100 μm
- Dual modes:
1. XANES for oxidation state analysis and bond covalency
2. EXAFS for coordination number, types of donors, and interatomic distances
QuantumLeap – Laboratory XAS with Synchrotron-Like Performance
The QuantumLeap from Sigray represents a breakthrough in laboratory-scale instrumentation with the ability to achieve synchrotron-like performance without the need to go to a synchrotron. It successfully provides sub-eV high energy resolution XANES and high throughput XANES and EXAFS.
Sigray is able to achieve this level of performance using a host of patented and patent pending technologies including:
- Patented high brightness x-ray source with microfocus spot and produces multiple x-ray spectra
- Patent-pending acquisition technique which switches for XANES and EXAFS, enabled by modern crystal/detector technology
- Proprietary double parabolic high efficiency x-ray optics with cut-off energy
As well as a rethink of the conventional experimental approach.
X-ray absorption spectroscopy looks at the change in absorption as a function of electronic/chemical states. It involves analyzing the changes in transmission of X-rays at energies near the absorption energy of an element of interest e.g. 8keV for copper.
[insert XAS spectrum graphic]
XANES – X-ray Absorption Near Edge Structure
XANES refers to changes in transmission of X-rays in the region near the absorption edge. These changes are predominantly the result of local atomic scattering. It is also sometimes called Near Edge X-ray absorption Fine Structure (NEXAFS)
It provides information about:
- Chemical/valence states e.g. oxidation state
- Co-ordination environment
EXAFS – Extended X-Ray Absorption Fine Structure
EXAFS looks at the region immediately above the absorption edge. This region consists of gentle oscillations caused by interference from neighbouring atoms.
[insert EXAFS spectrum]
It provides information about:
- Interatomic distance
- Number of neighboring atoms
- Nature of neighboring atoms (e.g. atomic number)
- Coordination number (number of atoms at specific distance)
Provided below is data generated using the Sigray QuantumLeap that demonstrates its ability to provide high resolution (sub-eV) XANEs and high throughput (within seconds EXAFS). Results for Fe were produced at 0.2eV energy resolution and are in excellent agreement with synchrotron data.
XAS is highly relevant to a number of fields including:
- Batteries/fuel cells/solar cells – the oxidation state of transition metals (e.g. in lithium ion batteries) as a function of charge and discharge cycles is of great interest to materials researchers in the energy sector
- Catalysts – chemical states of oxides, nitrides, and carbides with potential applications catalysts
- Nanoparticles and nanomaterials – structural analysis, coordination number, disorder, geometry, reactivity
- Geosciences – Mineralogic determination