Processes in the X-ray interferometer: The path of a single photon (pink) passes through two slits simultaneously and spreads out behind them into a characteristic “interference pattern”. This pattern is used to determine the strength of light refraction caused by the iron atoms (red) located in one of the two slits.
Photo Credit: Markus Osterhoff
Scientific Frontline: Extended "At a Glance" Summary: Nanoscale X-ray Interferometry
The Core Concept: A newly developed miniature X-ray interferometer, featuring slits separated by a mere 50 nanometers, enables researchers to precisely measure the refraction of X-rays and deduce their interactions with atomic nuclei.
Key Distinction/Mechanism: Unlike traditional interferometers, this device operates on a nanoscale by utilizing single X-ray photons passing through a double-slit setup. Atoms of the iron isotope ^57^Fe are placed in one slit, causing a slight refraction that produces characteristic interference patterns, which reveal the precise strength of the X-ray-matter interaction.
Major Frameworks/Components:
- Nanoscale Double-Slit Apparatus: A physical barrier with two slits spaced roughly one-thousandth the thickness of a human hair.
- Single-Photon Quantum Mechanics: The experiment primarily utilizes single X-ray photons to observe quantum wave-particle duality and phase shifts.
- Atomic Resonance Measurement: Exploiting specific atomic resonances by isolating the interaction between X-ray photons and ^57^Fe atomic nuclei.
Branch of Science: X-ray Physics, Quantum Mechanics, Nanophotonics.
Future Application: The foundation laid by this research paves the way for "integrated optical circuits" that operate using X-rays. It also has the potential to systematically map the refractive indices of various elements for advanced X-ray phase-contrast imaging, allowing for highly detailed 3D imaging of biological samples without damaging them.
Why It Matters: X-ray wavelengths are thousands of times shorter than visible light, making their slight refraction exceedingly difficult to measure. This breakthrough grants scientists unprecedented access to how X-ray light interacts with matter at the sub-atomic level, providing critical information about atomic arrangements that cannot be deduced from conventional light attenuation measurements.
A rainbow reveals with colors what otherwise remains hidden: light is “refracted” by transparent matter, in this case water droplets. This same physical effect underlies many everyday technologies, like LCD screens and broadband connections based on fiber-optic cables. Light refraction is caused by an interaction between light and the atoms of matter. This brings the light waves slightly out of sync, so to speak. “X-ray light” is “refracted”, too. But the effect is difficult to measure here. A miniature device now offers a novel approach: Researchers from the Universities of Göttingen and Hamburg, together with partners, have built the world's smallest X-ray interferometer, to their knowledge. It has enabled them to precisely measure, for the first time, the refraction of X-rays confined to a few nanometers, and to deduce how they interact with atomic nuclei. The study was published in the journal Nature Photonics.
The new X-ray interferometer is based on the famous double-slit experiment, which Nobel laureate Richard Feynman said, “has in it the heart of quantum mechanics”. “Our X-ray interferometer is probably the smallest interferometer in the world: The two slits are only 50 nanometers apart; that is roughly one-thousandth of the thickness of a human hair”, says lead author Dr Leon M. Lohse, who conducted the study at the University of Hamburg and works as a researcher at Göttingen University now. The researchers carried out experiments at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.
They placed atoms of the iron isotope 57Fe into one of the two slits. “The fascinating thing is that we carried out our experiment largely using single X-ray photons,” explains Lohse. Each of these “light particles” passes through both slits at the same time. In one slit, the photon interacts with the atomic nuclei of the iron isotope. It then produces characteristic patterns behind the slits, revealing how much the light is refracted. From the strength of light refraction, the researchers were able to draw conclusions about the interaction between the X-ray photons and iron atoms.
Building interferometers for X-rays is challenging. They must be exceptionally precise because “X-ray light waves” are refracted only slightly and they are extremely short – about a thousand times shorter than those of visible light and even shorter than the typical distance between atoms in matter. At the same time, their refraction is highly relevant. For example, it is used in X-ray phase-contrast imaging to generate detailed 3D images of biological samples without damaging them. It also provides information about the atoms contained in matter and how they are arranged – details that have been difficult for researchers to access until now.
“Our experiment opens up numerous avenues of research,” explains Professor Tim Salditt of Göttingen University. “It demonstrates how light refraction provides information that doesn’t emerge from the usually measured attenuation of light – particularly in connection with atomic resonances.” It also lays a foundation to measure the refractive index of different elements for X-rays systematically and precisely. “Integrated optical circuits” for X-rays could be possible in the future, too, the team envisions.
Published in journal: Nature Photonics
Title: Interferometric measurement of nuclear resonant phase shift with a nanoscale Young double waveguide
Authors: Leon M. Lohse, Ankita Negi, Markus Osterhoff, Paul Meyer, Sergey Yaroslavtsev, Aleksandr I. Chumakov, Lars Bocklage, Ralf Röhlsberger, and Tim Salditt
Source/Credit: Georg-August-Universität Göttingen
Reference Number: phy042026_01