Wikipedia:Today's second feature/October 1, 2005
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![Plasma lamp electrode and plasma stream](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Energy_Arc_%28central_electrode_of_a_Plasma_Lamp%29.jpg/250px-Energy_Arc_%28central_electrode_of_a_Plasma_Lamp%29.jpg)
The central electrode of a plasma lamp, showing a glowing blue plasma streaming upwards. The colors are a result of the radiative recombination of electrons and ions and the relaxation of electrons in excited states back to lower energy states. These processes emit light in a spectrum characteristic of the gas being excited.
Photo credit: PiccoloNamek