Emissivity of Water Vapor at 1200°K in the 19- and 27-µ Regions*

Abstract

The emissivities of the two bands of water vapor at 1.9 and 2.7 μ were determined at elevated temperatures. Use was made of quartz absorption cells of various lengths, which were heated in an electrical furnace to a temperature of 1200°K. By applying the “statistical” spectral-band model at every frequency in low-resolution spectra (8 cm−1), it was possible to obtain the band parameters x/L and 2πγ0/d and thus to correlate the observed spectral absorptance with the optical path length and the pressure of the gas. From absorptance measurements in the “linear region” the absolute intensity of the bands was derived. The total emissivity was calculated as a function of path length and pressure, and good agreement was obtained with direct observations of total emissivity at 1200°K.