helium-neon laser

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A laser in which the medium is a mixture of helium and neon in the mole ratio 1:5 respectively. An electric discharge is used to excite a He atom to the metastable 1s12s1 configuration. Since the excitation energy coincides with an excitation energy of neon, transfer of energy between helium and neon atoms can readily occur during collisions. These collisions lead to highly excited neon atoms with unoccupied lower energy states. Thus, population inversion occurs giving rise to laser action with a wavelength of 633 nm. (Many other spectral lines are also produced in the process.)

Subjects: Chemistry.

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