Measurement of the continuum absorption coefficient of water vapor near 14400 cm−1 (0.694 μm)

Abstract

The continuum absorption coefficient (CAC) of water vapor (k cont) in the visible region is determined for the first time from the data of laboratory measurements. For this purpose, the absorption spectra of water vapor in the region 14395–14402 cm−1 are recorded with the aid of a high-sensitivity photoacoustic spectrometer with a frequency-tunable single-pulse ruby laser, and the absorption measured in this transparency microwindow is compared with that calculated based on the HITRAN 2004 data bank. In the spectral region under study, k cont = (0.53 ± 0.18) × 10−9 cm−1 mbar−1 at a total pressure of a water vapor-nitrogen mixture of 1000 mbar and a temperature of 295 K. This value of the CAC is roughly 23% higher than the CAC value in the IO-CKD model of the continuum.