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Updated: Jun 25, 2026

Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy
Published on: December 1, 2023
Reading molecular messages from high-order harmonic spectra at different orientation angles
1Department of Physics, Centre for Nonlinear Studies, and The Beijing-Hong Kong-Singapore Joint Centre for Nonlinear and Complex Systems (Hong Kong), Hong Kong Baptist University, Kowloon Tong, Hong Kong, China. yjchen@hkbu.edu.hk
High-order harmonic generation (HHG) in hydrogen molecules depends on orientation and internuclear distance. A unique spectral intersection phenomenon reveals intramolecular two-center interference, probing molecular structure.
Area of Science:
- Quantum optics
- Molecular physics
- Attosecond science
Background:
- High-order harmonic generation (HHG) is a key process for generating ultrashort light pulses.
- Understanding molecular HHG is crucial for attosecond molecular dynamics studies.
Purpose of the Study:
- Investigate the orientation dependence of HHG in H(2)(+) with varying internuclear distances.
- Identify and analyze the spectral intersection phenomenon in molecular HHG.
Main Methods:
- Numerical and analytical calculations of HHG spectra.
- Simulations considering molecular axis orientation and internuclear separation.
- Analysis of spectral envelope intersections.
Main Results:
- HHG spectra are sensitive to molecular orientation and internuclear separation.
- A distinct spectral intersection occurs at specific harmonic orders.
- The intersection's position depends strongly on internuclear separation, not laser intensity.
Conclusions:
- The "intersection" phenomenon arises from intramolecular two-center interference.
- This phenomenon provides a novel method to probe the instantaneous molecular structure of H(2)(+).
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