Sci-fi Science: Transparent Aluminum

UV-Transparent Aluminum

Matter matters, and no kind of matter matters more than new states of matter. Did that sentence turn your brain to jelly? Good, because your noggin’s going to need to be extra stretchy in order to wrap around this über-crazy discovery. Just a few days ago, a research team from Oxford University’s Department of Physics proudly announced in the journal Nature Physics that they had created transparent aluminum. Moreover, they are calling the transparent state of the aluminum a brand-new state of matter, adding to the currently known solid, liquid, gas, and plasma states (as well as some lesser known theoretical or exotic states).

The team used a massive x-ray laser to blast the craaap (the scientific term) out of an incredibly thin aluminum foil specimen. To achieve a sufficiently large laser pulse, Germany’s FLASH laser (pictured above) was used. It’s actually a ~10 GW particle accelerator that can be tweaked to output a coherent beam of radiation. To put it in perspective, you could run eight DeLoreans on that much power.

The intensity of the x-ray burst was so great that it knocked an inner electron (from the L-shell, to be precise) clean out of orbit of every aluminum atom in its path. Since electrons are the parts of matter that actually interact with light and other forms of radiation and determine a material’s optical properties, this drastic alteration of aluminum’s electronic structure made the specimen completely transparent to ultraviolet light. Because the crystallographic structure of the aluminum wasn’t affected by the stripping of the electrons, the specimen was technically still regular ol’ aluminum and fundamentally unchanged aside from this limited transparency.

Here’s the catch, though: after the x-ray pulse, the aluminum only remained transparent for 40 femtoseconds. That’s 40 quadrillionths of a second, a duration so short the phenomenon could only be measured by extremely sensitive radiation sensors. After that time, the instability of the state is too great for it to be sustained and electrons return to their original positions. Even so, the material already holds great promise for various optical applications. If the procedure could be altered to selectively remove electrons from different orbitals, the aluminum could theoretically be made transparent to visible light too, making it true transparent aluminum. Of course, we’ll still need to address that 40 femtosecond issue…

So there you have it, folks. Transparent aluminum. Sort of. Perhaps it’s not quite here yet, but science is laying its foundations. But what if it were here today? What kind of interesting/wacky applications for it could you come up with? I’m partial to the idea of bulletproof hummingbird feeders, myself. Why?  Exactly!

ALON Product Info [Surmet]
Transparent aluminum is ‘new state of matter’ [University of Oxford]
FLASH Facility [DESY]

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