The authors designed an improved wedge shaped cell for measuring Lambert absorption coefficient spectra α(ν) of highly absorbent liquids. The design allows for accurate determination of the apex angle of the wedge, sealing the cell, and injection of the liquid without disassembling the cell. They measured α(ν) for water through the 500-12500cm-1 wavenumber region to determine the range of α(\nu) for which the cell provided accurate measurements. They then determined the imaginary part of the complex refractive index N(ν)=n(ν)+ik(ν) from α(ν) and used Kramers-Kronig methods to compute n(ν) from k(ν).

D. M. Wieliczka, S. Weng, M. R. Querry, "Wedge shaped cell for highly absorbent liquids: infrared optical constants of water," Appl. Opt.,28, 1714-1719 (1989).