Water-vapor continuum absorption in the 800–1250 cm −1 spectral region at temperatures from 311 to 363 K

Abstract

About 200 pure water-vapor spectra covering the region from 800 to 3500 cm −1 were recorded with resolution of 0.1 cm −1 at temperatures 311, 318, 325, 339, 352, and 363 K using a 2 m base White cell coupled to the BOMEM DA3.002 FTIR spectrometer. The water-vapor pressure varied from 28 to 151 mbar (21–113 Torr). Under these conditions, the continuum absorbance is quite measurable with the available path lengths up to 116 m. A program was developed for spectral processing that calculates, fits, and removes ro-vibrational structure from the spectrum. The spectra obtained were used to retrieve averaged and smoothed binary absorption coefficients over the region from 800 to 1250 cm −1. Our continuum data extrapolated to room temperature are in reasonable agreement with the MT_CKD continuum model. But at higher temperatures the MT_CKD model provides very low values, which are up to 50% less than those experimentally measured.