Saturated absorption spectroscopy of M1 transitions of O2 near 764 nm

Magnetic dipole transitions of oxygen molecules, which span the microwave-to-infrared region, play a crucial role in remote sensing applications. However, accurately determining the parameters of these weak transitions has long been a challenge. In this work, we present a saturated absorption spectroscopy measurement of magnetic dipole transitions of ^16O₂ near 764 nm using a comb-locked cavity ring-down spectrometer. The Line positions of eight transitions in the P branch of the b{0. 16em{0ex}}^1₆^+{0. 16em{0ex}}^3₆^- (0, 0) band were determined with an accuracy of better than 3. 5 kHz under zero magnetic field, an improvement of two orders of magnitude over previous studies. Zeeman splittings induced by the Earth's geomagnetic field were partially resolved, and their influence on the spectral line profile was meticulously analyzed using the Stokes matrix formalism. The results of this study also indicate the potential for the experimental determination of the Land\'e g factors of the energies of O₂ with better accuracy.