Abstract

The refractive index of water vapor for wavelengths in the infrared windows is important for laser techniques of distance measurement. Our own interest in this refractive index is the prediction of turbulence-induced scintillation in atmospheric propagation of infrared radiation. The refractive index of water vapor is calculated by line-by-line summation using the AFGL line parameters compilation. The calculation is performed at nine wavelengths between 19 and 7.8 µm, and three wavelengths near 3.4 µm. A simple formula for its dispersion and temperature dependence is given. We compare the line-by-line summation against measurements of refractive index for wavelengths near 10.6 and 3.4 µm. The calculations are in good agreement with data. The line-by-line calculation is also performed at visible wavelengths so that the infrared-resonance contribution to the refractive index in the visible may be subtracted from the empirical values thereby giving the ultraviolet-resonance contribution. The extrapolation of this UV-resonance refractive index from the visible to the infrared is shown to have an estimated uncertainty of two parts per thousand.

© 1986 Optical Society of America