Cavity ringdown spectroscopy measurements of the infrared water vapor continuum

We report measurements of the water vapor continuum using infrared cavity ringdown spectroscopy at frequencies of 931.002, 944.195, and 969.104 cm−1. Our values of the water vapor continuum coefficients for self-broadening at T=296 K are Cs0 (931 cm−1)=2.23±0.17, Cs0(944 cm−1)=2.02±0.13, and Cs0(969 cm−1)=1.79±0.21×10−22 molecules−1 cm2 atm−1. Our measurements are found to be in good agreement with the far wing line shape theory of Ma and Tipping, but we find that empirical models of the water vapor continuum, widely used in radiative transfer calculations, significantly overestimate the observed self-broadened continuum.