About 200 pure water-vapor spectra covering the region from 800 cm-1 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 DA8.002 FTIR spectrometer. The water-vapor pressure varied from 28 to 151 mbar (21 to 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 cm-1 to 1250 cm-1. Our continuum data extrapolated to room temperature are in reasonable agreement with the CKD continuum model. But at higher temperatures the CKD model provides very low values, which are up to 50% less than those experimentally measured.
Citation: Journal of Quantitative Spectroscopy and Radiative Transfer
Pub Type: Journals
calibration, hyperspectral, medical imaging, stray light