Germany's New Minister Steps Out of Shadow

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Science  29 Jan 1999:
Vol. 283, Issue 5402, pp. 601b
DOI: 10.1126/science.283.5402.601b

In conventional fluorescent lamps, ultraviolet (UV) emission from hot mercury vapor excites the phosphor lining the tube, which then emits visible light. Although the conversion is efficient (about 90% on a per photon basis), the use of mercury poses environmental problems, and its vaporization leads to delay in turning on a fluorescent lamp. Wegh et al. (p. 663; see the news story by Antia) show that mercury can be replaced with an inert gas, xenon, by using a phosphor that combines rare-earth lanthanide atoms that can efficiently transfer the energy between each other. A quantum efficiency of nearly 200% can be achieved because this downconversion process creates two visible photons from a single high-energy UV photon.

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