population inversion

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population inversion

[‚päp·yə′lā·shən in‚vər·zhən]
(atomic physics)
The condition in which a higher energy state in an atomic system is more heavily populated with electrons than a lower energy state of the same system.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Population Inversion


in physics, a state of a substance in which the higher energy levels of the constituent particles (such as atoms or molecules) are more “populated” by particles than are the lower levels. Under ordinary conditions (at thermal equilibrium) the inverse relation exists: there are fewer particles at the higher levels than at lower levels.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

population inversion

The condition that occurs when a material is radiated with another material at a certain wavelength, causing electrons to jump to a higher orbit (higher shell). When the electrons return to their ground state, they spontaneously emit a photon. Population inversion is the reason a laser works. The spontaneous emission of photons is amplified by mirrors causing a chain reaction and further stimulation of the excited atoms to release photons. See laser.
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References in periodicals archive ?
It implies that the population inversion can be controlled by proper choosing of fiber length and injected pump power to TDFA.
In Figure 1, we plot the dynamics of the atomic population inversion [[??].sub.z](t) as a function of the dimensionless time [lambda]t for different values of the atomic damping parameter [gamma]/[lambda] and the number of photon transition k.
Now, a team of physicists from the United States, Russia, and Germany have for the first time experimentally demonstrated laser oscillation without population inversion. The researchers take advantage of a quantum interference effect to generate a sustained laser beam of infrared light in a vapor of rubidium atoms.
Despite the fact that causes are involved in the capacity claim about atomic population inversion. some recent work has shown that its presence is not the only cause of lasing phenomena.

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