population inversion


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Related to population inversion: laser

population inversion

n.
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, require population inversion in order to generate radiation.
References in periodicals archive ?
b): Impulsive phase control of resonant gain and absorption represents a disruptive key technology rivalling the LASER especially in the hard-x-ray domain, where long-lived population inversion in dense media seems impossible.
The result is a population inversion in which there are more particles in the higher-energy state than in the ground state.
This state filling and emptying, called population inversion, is essential for laser action and was achieved by tunneling, a counter-intuitive quantum-mechanical process by which electrons can traverse ultrathin (nanometer-thick) barriers even when they have an energy too small to surmount it.
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