Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques

Area of Science:

• Molecular Spectroscopy
• Quantum Optics
• Physical Chemistry

Background:

• Accurate molecular transition frequencies are crucial for various scientific applications, including metrology and atmospheric sensing.
• Previous measurements of carbon monoxide (CO) transitions had limitations in precision and accuracy.

Purpose of the Study:

• To measure absolute frequencies of unperturbed (12)C(16)O transitions in the near-infrared (3-0) band with significantly improved accuracy.
• To demonstrate the capability of cavity-enhanced spectroscopic methods for high-precision molecular measurements.
• To establish a new benchmark for molecular spectroscopy linked to primary frequency standards.

Main Methods:

• Utilized three cavity-enhanced spectroscopic techniques: frequency-stabilized cavity ring-down spectroscopy, cavity mode-width spectroscopy, and one-dimensional cavity mode-dispersion spectroscopy.
• Linked the frequency axis of all spectra to the primary frequency standard.
• Employed various data analysis approaches to identify and minimize systematic instrumental errors.

Main Results:

• Achieved uncertainties five-fold lower than previously available data for absolute frequencies of unperturbed (12)C(16)O transitions.
• Obtained line positions for Doppler-broadened R24 and R28 transitions with relative uncertainties at the 10⁻¹⁰ level.
• Demonstrated the highest quality dispersion line shape measured in optical spectroscopy to date.

Conclusions:

• The study presents the first demonstration of molecular spectroscopy where both spectral axes are directly linked to the primary frequency standard.
• The achieved precision and accuracy pave the way for future reference-grade measurements of molecular spectra.
• The developed methods and results are highly valuable for advancing precision measurements in molecular physics and chemistry.