Absolute frequency metrology of the CHF3 8.6-mu m ro-vibrational spectrum at 10(-11) level

An optical-frequency-comb-referenced quantum cascade laser is used to perform wavelength-modulation Lamb-dip spectroscopy on a large number of ro-vibrational transitions falling in the CHF3 upsilon(5) fundamental band at 8.6 mu m. The combined (statistical + systematic) fractional uncertainty in the absolute determination of the line-center frequencies ranges from 9 x 10(-11) down to 2 x 10(-11). This represents an improvement by more than two orders of magnitude, as compared to a recent and extensive study performed with a high-resolution FTIR spectrometer [1]. Our investigation realizes a sharpened knowledge of the CHF3 spectrum over a wide interval, also managing to accurately determine the positions of very close, previously unresolved multiple ro-vibrational components. (C) 2020 Elsevier Ltd. All rights reserved.