Mid-Infrared line intensity for the fundamental (1–0) vibrational band of carbon monoxide (CO)

Here we apply cavity ring-down spectroscopy to measure the intensity of a rotational-vibrational transition within the fundamental (1–0) vibrational band of carbon monoxide (CO). Laser measurements were made at a wavenumber near 2206 cm⁻¹ on a sample of CO-in-air with an amount fraction of χ_CO = 77.6 nmol mol⁻¹. High-precision cavity ring-down spectra were acquired using hybrid amorphous-crystalline mirrors to form the optical resonator and by application of simple and robust laser scanning and control techniques. With a relative combined standard uncertainty of u_S = 0.6 %, we report the R17 line intensity for the fundamental (1–0) vibrational band of ¹²C¹⁶O to be S = 1.028 × 10⁻¹⁹ cm⁻¹ molecule⁻¹ (isotopologue abundance, χ_iso = 100 %; temperature, T = 296 K), a value which differs from HITRAN2020 by a relative amount of 2.2 %.