Monitoring ultrafast vibrational dynamics of isotopic molecules with frequency modulation of high-order harmonics.
basic_science · Level V
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- Record sourced from PubMed, PMID 29549255.
- Also identified by DOI 10.1038/s41467-018-03568-3 and PMC identifier 5856770.
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Abstract
Molecules constituted by different isotopes are different in vibrational modes, making it possible to elucidate the mechanism of a chemical reaction via the kinetic isotope effect. However, the real-time observation of the vibrational motion of isotopic nuclei in molecules is still challenging due to its ultrashort time scale. Here we demonstrate a method to monitor the nuclear vibration of isotopic molecules with the frequency modulation of high-order harmonic generation (HHG) during the laser-molecule interaction. In the proof-of-principle experiment, we report a red shift in HHG from H<sub>2</sub> and D<sub>2</sub>. The red shift is ascribed to dominant HHG from the stretched isotopic molecules at the trailing edge of the laser pulse. By utilizing the observed frequency shift, the laser-driven nuclear vibrations of H<sub>2</sub> and D<sub>2</sub> are retrieved. These findings pave an accessible route toward monitoring the ultrafast nuclear dynamics and even tracing a chemical reaction in real time.