Absolute frequencies of water lines near 790 nm with 10−11 accuracy

- Several water lines near 790 nm, in the 013-000 band of H216O are recorded with comb-locked cavity ring-down saturation spectroscopy.
- Line positions are determined with an uncertainty of 25 kHz (relatively 6.6 × 10−11), over one order of magnitude more accurate in a previous study.
- Upper energies of these transitions are determined with an accuracy of 10−6 cm−1, indicating that the IUPAC-reported energies are inaccurate within 0.001 cm−1.

Water lines in the infrared are convenient frequency references. We present absolute positions of several H216O ro-vibrational transitions around 790 nm using comb-locked cavity ring-down saturation spectroscopy. Lamb dips of 6 water lines with saturation power in the range of 70-130 kW/cm2 were observed and the line positions were determined with an accuracy of 25 kHz, corresponding to a fractional uncertainty of 6.6 × 10−11. The present work demonstrates the capability to considerably improve the accuracy of the water line positions in the infrared.

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