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population inversion
noun
, Physics.
- a condition of matter in which more electrons are in a high energy state than in a lower energy state, as is required for the operation of a laser.
population inversion
- The condition of having enough excited or high-energy states distributed throughout a substance to sustain a chain-reaction of stimulated emission. Lasers, for example, need a constant power source that maintains population inversion in order to generate radiation continuously, since each stimulated emission reduces the population of high-energy states.
- See also stimulated emission
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Word History and Origins
Origin of population inversion1
First recorded in 1960–65
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Example Sentences
Working to enable the precursor of the laser — the maser — he found a practical way to generate a population inversion, an unusual situation in which more members of a physical system exist at a higher energy level than at a lower one.
From Nature
Population inversion is a prerequisite for lasers, and Bloembergen's scheme, three-level pumping, enabled the development and widespread adoption of the laser.
From Nature
Lasers ordinarily require a population inversion, a condition in which atoms in an excited state outnumber those in the ground state; the excited atoms emit laser photons as they drop to the ground state.
From Scientific American
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