Researchers have demonstrated a new X-ray technique that can use a single optical component to create detailed images and visualize a material’s chemical properties, potentially making advanced X-ray experiments faster and easier.
The study showed that the approach could image circular samples about 27 times faster than a traditional point-by-point scan, while also capturing a full spectroscopy data set in about 220 seconds.
Instead of relying on multiple optical elements, the researchers used a reflective zone plate (RZP). This precisely nanostructured reflection optics can simultaneously reflect, focus and separate soft X-rays.
The international team from Germany, Switzerland and Japan carried out the experiments on beamline P04 of the synchrotron radiation source PETRA III at DESY in Hamburg.
Narrow X-ray beam creates 2D image
Standard X-ray imaging reveals the shape and location of features within a sample, while spectroscopy provides information about its chemical composition, electronic structure and molecular bonding. Combining both techniques typically requires multiple optical components that must be carefully aligned, the researchers noted. In the new approach, the RZP takes over all of these functions in a single, compact system.
To test whether the system could produce clear images, the researchers first examined standard test patterns containing Siemens stars, star-shaped targets commonly used to measure image sharpness, and the letters “RIXS.”
Instead of scanning one tiny spot at a time, the team illuminated the sample with a narrow X-ray line. The team then moved the sample across the beam in small increments, like a document running through a scanner. A computer stitched together the individual strips of images to create a complete two-dimensional image.
The technique resolved features measuring about 14 to 24 micrometers (μm), many times smaller than the width of a human hair. Because the system scanned an entire line rather than individual points, it was able to image circular objects about 27 times faster while maintaining comparable image quality.
Distortion-free images
The researchers said the achievement was remarkable because such imaging was previously considered unfeasible due to Abbe sinus condition. This optical principle predicts image distortions under certain conditions. They overcame the problem by operating the reflection zone plate in the paraxial region, so that it could only collect X-rays propagating within a narrow angular range. This reduced optical distortion and enabled larger objects to be imaged sharply.
“The strong scattering of the RZP enables the simultaneous measurement of multiple spectroscopic features,” said Dr. Christoph Braig. “What is important is that both the elastic and inelastic signals can be recorded in the same optical configuration.”
After testing the imaging method, the team replaced the test sample with a thin beam of acetonitrile dissolved in ethanol to demonstrate chemical analysis. Instead of illuminating the sample with a single X-ray energy, they used a beam that contained many energies at once, creating what the researchers called an X-ray “rainbow.”
The RZP simultaneously measured the energies of incoming and outgoing X-rays, allowing researchers to capture a complete two-dimensional map of resonant inelastic X-ray scattering (RIXS) without changing the experimental system. The system recorded emitted X-rays between 388.6 and 401.8 electron volts (eV) and resolved elastic, inelastic and vibrational features near the nitrogen K-edge. The entire data set was acquired in approximately 220 seconds, significantly faster than standard methods.
“Our experiments show that an RZP with a compact optical arrangement can provide both spatial and spectroscopic information,” said Jens Rehanek. “This could make advanced soft X-ray measurements more efficient and easier to implement.”
Lead and corresponding author Zhong Yin of the Synchrotron Radiation Instrumentation Science Laboratory (SRIS) at Tohoku University said the combination of reflection, focusing, imaging and spectral dispersion in a single optical element provides “a compact and efficient route to soft X-ray spectromicroscopy” and can open up new possibilities for studying materials at the atomic level.
The results were published in Optic Express.
