High-accuracy CO line intensities in the 2 μm wavelength region measured by frequency-stabilized cavity ring-down spectroscopy.

Reported here are highly accurate, experimentally measured ro-vibrational transition intensities for the R-branch of the (20012) - (00001) CO band near = 2 μm. Measurements were performed by a frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) instrument designed to achieve precision molecular spectroscopy in this important region of the infrared. Through careful control and traceable characterization of CO sample conditions, and through high-fidelity measurements spanning several months in time, we achieve relative standard uncertainties for the reported transition intensities between 0.15 % and 0.46 %. Such high accuracy spectroscopy is shown to provide a stringent test of calculated potential energy and dipole moment surfaces, and therefore transition intensities calculated from first principles.