Ultra-sensitive optical measurements of high-J transitions in the O2 A-band

We report frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) measurements of high-J O2 A-band magnetic dipole line parameters. Our goals were to measure intensities and line shape parameters for the primary isotopologue of O2 in the A-band region and to understand how these quantities compare to, and build on those contained in the Hitran database. These experiments quantify line parameters of some of the weakest transitions ever observed in the laboratory. We have measured line intensities as low as 1 × 10−30 cm molecule−1. Our data extend available data in the P-branch up to J′ = 50. Additionally, we have characterized the self-broadened and air-broadened line widths and provide new J-dependent correlation functions.