By use of a wedge-shaped cell providing an absorbing layer tapering in thickness from less than one wavelength of visible light at one end to approximately 20µm at the other end, we have measured the Lambert absorption coefficient for water in the spectral region between 4000 and 288 cm-1. After proper initial alignment of the cell windows had been established by the observation of interference fringes in the visible, we measured film thicknesses at various positions along the wedge by interferometric methods, employing convenient wavelengths in the infrared. We present the results of the study in graphical and tabular form.
CHARLES W. ROBERTSON and DUDLEY WILLIAMS, "Lambert Absorption Coefficients of Water in the Infrared," J. Opt. Soc. Am. 61, 1316-1320 (1971)