We just reported a few weeks ago on the successful masking of objects from microwaves. Now a research team from Hamburg, Germany has figured out how to make iron (57Fe) transparent to X-rays -- and presumably Superman.
A team of researchers from Deutsches Elektronen-Synchrotron (DESY) in Germany made the discovery by employing a technique known as electromagnetically induced transparency (EIT) -- this is when an object's nuclei's emission and absorption of energy are in equilibrium. At this point, each iron nucleus is in resonance, but more about that in a second.
The experiment took place in an optical resonance chamber. Two sheets of iron are affixed at a precise distance apart within the chamber and affixed with a layer of carbon. X-rays shoot through the chamber and bounce off a pair of platinum mirrors, until they create a standing wave. As the iron nuclei absorb and then reemit the X-ray energy, the nucleus of the atom begins to cycle back and forth between two fixed energy levels (similar to how electrons jump between energy shells). When the nucleus absorbs the X-ray, it moves to a higher energy and when it emits it, the nucleus moves back down in energy.
If the sheets are placed the correct distance apart to acheive total destructive interference, the X-ray photons in the standing wave will cancel each other out and the X-ray beams travel through the chamber unimpeded. Basically, at the correct distance, the nucleus is spitting out X-ray photons at exactly the same speed as it's absorbing them, which makes it appear invisible in the X-ray spectrum.
This has an added benefit of drastically slowing down the X-ray photons. In a vacuum they travel 300 million meters per second but through the iron, they travel just 30 meters per second. The team hopes to someday harness the nuclei's resonance, they hope to manipulate X-rays as easily as visible light. [Nature via Ars Technica]
Image: Deutsches Elektronen-Synchrotron (DESY)