A tunable far infrared optically pumped laser has been used to measure the reflection <i>R</i> and transmission of liquid water at 25°C. The laser covered the range 8.22–175.7 cm<sup>- 1</sup> with an average spacing between lines of 8 cm<sup>- 1</sup>. The optical data were used to find the complex index of refraction <i>nik</i> with typical errors of 2%. A small peak in n was observed near 55 cm<sup>- 1</sup>. This feature correlates with published Raman data. The values of <i>R</i>, <i>n</i>, <i>k</i>, and the absorption coefficient α are given in graphical and tabular form.
© 1980 Optical Society of AmericaPDF Article