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Updated: May 10, 2026

Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Indirect rotational spectroscopy of HCO+
Brian M Siller1, James N Hodges, Adam J Perry
1Department of Chemistry and ‡Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
High-precision spectroscopy of the HCO+ ion was achieved using an optical frequency comb. This enables accurate astronomical detection of the ν1 vibrationally excited state, advancing astrochemistry research.
Area of Science:
- Molecular Spectroscopy
- Astrochemistry
- Quantum Optics
Background:
- The formyl cation (HCO+) is a crucial molecule in interstellar chemistry.
- Accurate spectroscopic data is vital for detecting and understanding HCO+ in astronomical environments.
Purpose of the Study:
- To perform high-resolution spectroscopy of the ν1 band of HCO+.
- To precisely determine the rotational spectrum of the ν1 vibrationally excited state of HCO+.
- To assess the potential for astronomical detection of this excited state.
Main Methods:
- Utilized an optical parametric oscillator (OPO) calibrated by an optical frequency comb for sub-MHz accuracy spectroscopy.
- Applied combination differences analysis to rovibrational data to validate accuracy against known ground-state transitions.
- Employed cavity-enhanced sub-Doppler spectroscopy for enhanced precision.
Main Results:
- Achieved sub-MHz accuracy in the spectroscopy of the HCO+ ν1 band.
- Calculated the previously unobserved rotational spectrum of the ν1 vibrationally excited state with high precision.
- Demonstrated the feasibility of astronomical detection for this excited state.
Conclusions:
- The employed spectroscopic technique provides unprecedented accuracy for studying astrophysically relevant ions.
- The precise spectral data facilitates the identification and characterization of HCO+ in interstellar space.
- Future cavity-enhanced spectroscopy promises even higher accuracy and precision.
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