High-order harmonic transient grating spectroscopy of SF6 molecular vibrations

Amélie Ferré, David Staedter, Frédéric Burgy, Michal Dagan, Dominique Descamps, Nirit Dudovich, Stéphane Petit, Hadas Soifer, Valérie Blanchet, Yann Mairesse

Research output: Contribution to journalArticlepeer-review

Abstract

Strong field transient grating spectroscopy has shown to be a very versatile tool in time-resolved molecular spectroscopy. Here we use this technique to investigate the high-order harmonic generation from SF6 molecules vibrationally excited by impulsive stimulated Raman scattering. Transient grating spectroscopy enables us to reveal clear modulations of the harmonic emission. This heterodyne detection shows that the harmonic emission generated between 14 and 26eV is mainly sensitive to two among the three active Raman modes in SF6, i.e. the strongest and fully symmetric υ1-A1g mode (774cm-1, 43 fs) and the slowest mode υ5-T2g (524cm-1, 63 fs). A time-frequency analysis of the harmonic emission reveals additional dynamics: the strength and central frequency of the υ1 mode oscillate with a frequency of 52cm-1 (640 fs). This could be a signature of the vibration of dimers in the generating medium. Harmonic 11 shows a remarkable behaviour, oscillating in the opposite phase, both on the fast (774cm -1) and slow (52cm-1) timescales, which indicates a strong modulation of the recombination matrix element as a function of the nuclear geometry. These results demonstrate that the high sensitivity of high-order harmonic generation to molecular vibrations, associated to the high sensitivity of transient grating spectroscopy, make their combination a unique tool to probe vibrational dynamics.

Original languageEnglish
Article number124023
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume47
Issue number12
DOIs
StatePublished - 28 Jun 2014
Externally publishedYes

Keywords

  • high-order harmonic generation
  • strong fields
  • sulfur hexafluoride
  • transient grating spectroscopy
  • vibrational wave packets

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