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Updated: Jun 5, 2026

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Recombination-pumped triatomic hydrogen infrared lasers
R J Saykally1, E A Michael, J Wang
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Abstract:
Mid-infrared laser lines observed in hydrogen/rare gas discharges are assigned to three-body recombination processes involving an electron, a rare gas (He or Ne) atom, and the triatomic hydrogen ion (H(3)(+)). Calculations of radiative transitions between neutral H(3) Rydberg states support this interpretation, and link it to recent results for hydrogenic∕rare gas afterglow plasmas. A mechanism for the population inversion is proposed, and the potential generality and astrophysical implications of such molecular recombination laser systems are briefly discussed.
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