OPTICAL CONSTANTS OF AMMONIUM SULFATE

Abstract

Atmospheric studies have revealed the existence of ammonium sulfate particles in the earth’s stratosphere. The scattering and absorption of solar infrared radiation by such particles can be calculated from Mie theory provided the optical constants $N = n + ik$ of ammonium sulfate are known. We have determined these constants from near-normal reflectance measurements and subsequent Kramers-Kronig analysis for aqueous solutions of 1.6, 2.4, 3.2, and 3.3 molar concentrations. The latter is the highest concentration achieved at room temperature. Curves of n($\nu$)-vs-$\nu$ and k($\nu$)-vs-$\nu$ for the spectral range $5000-400 cm^{-1}$ will be shown and the effects of the solute ions on the water structure will be discussed. While these studies may not confirm the existence of particular concentrations of ammonium sulfate in our atmosphere, we hope that our investigations will form the basis for future, studies of this aerosol.