Absolute frequency metrology of the CHF3 8.6-µm 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 υ5 fundamental band at 8.6 µm. The combined (statistical + systematic) fractional uncertainty in the absolute determination of the line-center frequencies ranges from 9×10−11 down to 2×10−11. 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.