Complex refractive index in the infrared for NaCl, NaNO_3, and NaHCO_3 in water*

Relative specular reflectances of individual 0.5M aqueous solutions of NaNO3, NaHCO3, NaCl, and of 0.25M NaCl were measured in the 500–5000 cm−1(2–20 μm) region of the infrared for linearly polarized radiant flux having the electric field vector perpendicular to the plane of incidence. Distilled water was the reflectance standard. The angle of incidence was 70.03° ± 0.23°. Kramers-Kronig analysis of the relative reflectance spectra provided phase-difference spectra for the aqueous solutions and a tabulation of spectral values for the complex refractive index n + ik. The strengths of selected infrared active vibrational bands of the molecular anions NO3− and HCO3− were determined by integrating values for their molecular extinction coefficients over spectral regions of the bands.