Forget fancy particle accelerators — a cheaper tool for emitting X-rays is right there in the office supply cabinet. Pulling back Scotch tape emits X-rays, the same high-energy light emanating from airport security scanners and the interiors of galaxy clusters, and scientists now have a better understanding of why.
Physicists were dumbfounded two years ago when UCLA researchers produced quick flashes of X-ray light by peeling Scotch tape in a vacuum. Scientists have known since the dawn of 3M Scotch tape in the 1930s that pulling the adhesive emits blue light. But to discover that X-rays also fly out was perplexing because X-rays are a hundred thousand times more energetic than the chemical bonds holding the sticky side down.
Not only that, says UCLA physicist Seth Putterman, the light can pulse a billion times a second from a region only 100 micrometers in size, or about the width of a human hair.
“Just try to purchase a device like this,” Putterman says. Now, two teams of scientists have an explanation: Peeling tape separates positive and negative charges, creating an electric field. The field jump-starts free electrons in the neighborhood, accelerating them fast enough to emit X-ray photons. This bremsstrahlung radiation is like that created in the bellies of particle accelerators as they whip charged particles around near the speed of light.
No need to worry about radiation exposure at the office — at atmospheric pressure, where air molecules bustle, the electrons quickly run into other particles before they can radiate X-rays.