Molecular transition frequencies of CO2 near 1.6 µm with kHz-level uncertainties

We present measurements of molecular transition frequencies based on the comb-locked cavity ring-down spectroscopy technique, reporting vacuum Doppler-broadened 12C16O2 in 1.6 ?m region for (30012) ? (00001) and (30013) bands with an average combined standard uncertainty ? 1 kHz. A global four-state model was fit to these data literature values provide spectroscopic parameters a best-case precision 4 identified quantified interaction between (33301) states which manifest as observed Fermi-resonance-type perturbation band. This accounted fit, substantially reducing systematic uncertainties state altering many predicted band by MHz or more relative values. The accurate reported here may be considered SI-traceable reference diverse applications including remote sensing telecommunications.