Vibrational excitation of hydrogen molecules by two-photon absorption and third-harmonic generation

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Abstract

We report the coherent excitation of the vibrational state of hydrogen molecules by two-photon absorption and the resultant third-harmonic generation (THG). Parahydrogen molecules cooled by liquid nitrogen are irradiated by mid-infrared nanosecond pulses at 4.8 μm with a nearly Fourier-transform-limited linewidth. The first excited vibrational state of parahydrogen is populated by two-photon absorption of the mid-infrared photons. Because of the narrow linewidth of the mid-infrared pulses, coherence between the ground and excited states is sufficient to induce higher-order processes. Near-infrared photons from the THG are observed at 1.6 μm. The dependence of the intensity of the near-infrared radiation on mid-infrared pulse energy, target pressure, and cell length is determined. We used a simple formula for THG with consideration of realistic experimental conditions to explain the observed results.

Original languageEnglish
Article number015401
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume51
Issue number1
DOIs
Publication statusPublished - Jan 14 2018

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Keywords

  • hydrogen molecule
  • molecular vibration
  • third-harmonic generation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics

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