Element-specific insight into the local structure and electronic state of materials
X-ray absorption spectroscopy (XAS) is a powerful analytical technique used to study the local atomic structure and electronic state of materials. Unlike diffraction techniques that reveal long-range crystal structure, XAS provides element-specific information about the immediate environment surrounding individual atoms.
This makes XAS particularly valuable for investigating complex materials such as catalysts, battery electrodes, nanomaterials, and functional oxides.
XAS is widely used across disciplines, including materials science, chemistry, physics, environmental science, and biology. Traditionally, these experiments have been performed at synchrotron facilities due to their high-brightness X-ray sources. But access to these facilities is limited and beamtime is highly competitive, costing valuable time and resources.
With modern laboratory instrumentation such as the Empyrean, XAS measurements can now be performed directly in the laboratory, providing convenient access to advanced chemical and structural characterization.
In an X-ray absorption spectroscopy experiment, X-rays of a defined energy are directed onto a sample. When the energy of the incident X-rays matches the binding energy of a core electron in an atom, the electron is excited to an unoccupied state or ejected from the atom.
By measuring how strongly the sample absorbs X-rays as the energy is varied across an absorption edge, an XAS spectrum is obtained.
The absorption coefficient is determined by comparing the X-ray intensity measured with the sample and without the sample, and applying the Beer–Lambert law.
By scanning the incident X-ray energy across a range around the absorption edge, a detailed absorption spectrum is recorded. The fine structure within this spectrum contains information about the electronic structure and the arrangement of atoms surrounding the absorbing element.
An XAS spectrum consists of two main regions, each providing different structural information: X-ray absorption near-edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS).
Find out more about each of these below.
The region close to the absorption edge (typically within ~50 eV) is known as XANES.
XANES is highly sensitive to:
This makes XANES particularly useful for studying chemical state changes and redox processes.
Beyond the near-edge region lies the EXAFS region, which can extend several hundred electron volts above the absorption edge.
The oscillations observed in EXAFS arise from the interference between outgoing photoelectrons and waves scattered by neighboring atoms.
Analysis of these oscillations provides detailed information about:
EXAFS is therefore a powerful tool for determining the local structure of materials, even in systems lacking long-range order.
X-ray absorption spectroscopy (XAS) delivers detailed insights into the local chemical and structural environment of specific elements within a material.
Key information obtainable from XAS includes:
Because XAS is element-specific, it can selectively probe individual elements even in complex mixtures or multiphase materials.
Synchrotron facilities provide powerful X-ray sources, but access is often limited, and experiments must be scheduled well in advance.
Laboratory-based XAS enables researchers to:
With the Empyrean XAS, researchers gain flexible access to XAS directly in their own laboratory.
Discover how X-ray absorption spectroscopy supports research in key application areas:
Add local chemical insight to your multipurpose X-ray platform
XAS is now available exclusively on the Empyrean platform, so you can obtain synchrotron-level insights without leaving your lab. Empyrean uniquely combines advanced X-ray diffraction (XRD), X-ray scattering, imaging, and XAS on a single modular research platform.
An XAS-enabled Empyrean includes:
This unique integration enables researchers to obtain both structural and electronic information, all from a single instrument platform, including phase identification and quantification