F-Center

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An F-Center, from the German Farbenzentrum, or color center, is the anionic vacancy in a crystal filled by one or more electrons (depending on the charge of the missing ion in the crystal). The electron has a series of energy levels. It can absorb light and jump to excited states. When it falls back, it emits energy in the form of electromagnetic waves, e.g. light. This process is responsible for the color of a crystal. Template:Chem-stub