Triboluminescence; Sugar Coated.
Imagine you are traveling with the ancient Native American Ute shamans in the American Midwest, hunting for quartz crystals. After collecting the crystals and placing them into ceremonial rattles made of translucent buffalo skin, you wait for the night-time rituals to begin to summon the spirits of the dead. When it is dark, you shake the rattles and they blaze with flashes of light as the crystals collide with one another.
What is the cause of this ‘spiritualistic’ dance of light? Well, you are experiencing one of the oldest known applications of triboluminescence, a physical process through which the light is generated when materials are crushed, rubbed, and ripped—as electrical charges are separated and reunited. The resultant electrical discharge ionizes the nearby air, triggering flashes of light.
In 1620, the English scholar Francis Bacon published the first known documentation of the phenomena, in which he mentions that sugar will sparkle when “broken or scrapped” in the dark. This was also taught to me in my first chemistry lecture at University, it's an easy experiment to carry out at home by breaking sugar crystals in a dark room. Another experiment can be carried out with WintOgreen Lifesavers candy, the wintergreen oil (methyl salicylate) in the candy absorbs ultraviolet light produced by the crushing of sugar and reemits it as blue light.
The spectrum of light produced by sugar triboluminescence is the same as that for lightning. In both cases, electrical energy excites nitrogen molecules in the air and they're ready to party. Most of the light emitted by nitrogen in the air is in the ultraviolet range that our eyes cannot see, and only a small fraction is emitted in the visible range. When the sugar crystals are stressed (aggravated not agitated), positive and negative charges accumulate, finally causing electrons to jump across a crystal fracture and excite electrons in the nitrogen molecules.
Here is something else that’s cool: If you peel Scotch tape in the dark, you may also be able to see emitted light from triboluminescence. I haven’t tried this so guys, if you do, let me know the outcome! Interestingly, the process of peeling such tape in a vacuum can produce x-rays that are sufficiently strong to create an x-ray image of the finger! Of course, I haven’t tried this and I probably wouldn’t recommend anyone else doing so either.
Take home message: Scratching a sugar cube is sweet.
~ JM
Image Credit: http://bit.ly/1HeKruE
More Info: Triboluminescence short intro: http://bit.ly/1CElHFq
WintOgreen Candy experiment: http://bit.ly/1KI20l0
Triboluminescence with quartz: http://bit.ly/1FwsqIO
Triboluminescence in sticky tape:http://bit.ly/YTKqcG