Saturated Cavity Ring-Down Spectroscopy of ¹²C¹⁶O₂ near 1.57 μm

We present the saturated absorption spectroscopy of the 30012\leftarrow00001 band of ¹²C¹⁶O₂ by a comb-locked cavity ring-down spectrometer near 1.57 μm. Positions of 37 lines with rotational quantum numbers up to 68 were determined with an accuracy of a few kHz. Comparisons of the ro-vibrational energy levels determined in this work with the Doppler-limited experimental values from literature and those from the CDSD2019 databank are given. Deviations exceeding 1 MHz were observed in the transitions blended by other carbon dioxide isotopologues.