Exploring the invisible world through soft X-ray spectromicroscopy at the Swiss Light Source
Imagine if scientists could peer deep into the heart of a material and watch how individual molecules arrange themselves, or track the intricate magnetic dance within futuristic computer memory. At the Swiss Light Source (SLS) in Switzerland, a remarkable instrument called PolLux makes this possible.
Reveals not just where atoms are, but what they are and how they behave
Investigates magnetic phenomena through X-ray magnetic circular dichroism
Studies airborne particles that affect our health and climate
Soft X-rays occupy a specific range in the electromagnetic spectrum—with energies between 200 and 2000 electronvolts—positioned between the more familiar hard X-rays used in medical imaging and the far less energetic ultraviolet light. This particular energy range corresponds to the binding energies of electrons in the inner shells of atoms like carbon, nitrogen, oxygen, and various metals that are crucial to biological and material sciences 1 .
Approximately 1,000 times smaller than the width of a human hair
~25 nm resolution
Standard for routine operations with Fresnel Zone Plates
Sub-15 nm resolution
Required specialized zone plates and short focal distances
Single-digit nanometer regime
Ongoing development of zone plates with 6.4 nm features 3
Scientists used the X-ray spectromicroscopy capabilities at the PolLux beamline to investigate why certain airborne particles remain chemically active and potentially harmful over extended periods in our atmosphere 1 3 .
| Finding | Scientific Significance | Practical Implications |
|---|---|---|
| Viscous particles trap reactive compounds | Explains long-term persistence of harmful species in aerosols | Improves models of air pollution impacts and longevity |
| Low water content enables trapping | Identifies specific conditions that increase particle toxicity | Helps predict which atmospheric conditions produce most hazardous particles |
| Reactive oxygen species (ROS) persist inside particles | Reveals mechanism for prolonged chemical activity | Explains prolonged health effects after exposure to certain air pollutants |
| Light exposure maintains reactivity | Demonstrates how sunlight drives ongoing chemical reactions | Enhances understanding of atmospheric chemistry and pollution dynamics |
| Component | Function | Application in Research |
|---|---|---|
| Fresnel Zone Plates (FZP) | Focuses X-rays to a small spot through diffraction | Creates nanoscale beam for high-resolution scanning; recently achieved zone widths below 10 nm 3 |
| Central Stop (CS) | Blocks undiffracted zero-order radiation from the FZP | Prevents overpowering of focused beam flux and detector saturation 1 |
| Order-Selecting Aperture (OSA) | Removes higher diffraction orders from the FZP | Ensures only first-order focused beam illuminates the sample 1 |
| Pixelated Area Detector | Captures diffraction patterns with high dynamic range | Enables ptychographic reconstruction by recording scattered X-rays 1 |
| Scanning Stage | Moves sample with nanometer precision through the beam | Allows overlapping scan positions required for ptychography 1 |
This approach has several advantages over traditional scanning transmission X-ray microscopy (STXM). While STXM measures absorption point by point as the sample is raster-scanned through the beam focus, ptychography captures full diffraction patterns at each position, providing information about both the amplitude and phase of the transmitted X-rays 1 .
Researchers used PolLux's soft X-ray laminography technique to perform three-dimensional magnetic imaging of magnetic skyrmions—nanoscale vortex-like spin structures that exist in certain magnetic materials 3 .
Scientists demonstrated that magnetic skyrmions stabilized in ferrimagnetic heterostructures can be displaced by electrical currents at high velocities while exhibiting low deflection angles, suggesting excellent candidates for fast skyrmionic devices 3 .
By combining time-resolved soft X-ray imaging with magnetic laminography, researchers have investigated magnetization dynamics in ferromagnetic microstructures resolved in all three spatial dimensions and in time. This "fourth-dimensional" approach allows scientists to study resonant magneto-dynamical processes, such as magnetic vortex core gyration and switching, and spinwave emission—all critical phenomena for developing next-generation magnetic devices 3 .
The ongoing upgrade of the Swiss Light Source to SLS 2.0 promises even greater opportunities for scientific discovery. This upgrade will provide a more brilliant X-ray beam, enabling faster measurements with even higher resolution and sensitivity 1 .
What makes facilities like PolLux truly remarkable is their ability to make the invisible visible—to reveal the hidden patterns and processes that govern the behavior of matter at the smallest scales. By providing a window into this nanoscale universe, PolLux continues to expand the frontiers of scientific knowledge, enabling discoveries that will shape our understanding of the world and drive technological innovation for decades to come.