Absorption spectra of molecules adsorbed on light-scattering media. Part 1.—Absorption cross-section of the adsorbed molecules

Abstract

A theoretical approach to the absorption properties of molecules adsorbed on powdered solids is presented. Thus expressions for the reflectance and transmittance of the surface of coated particles with sizes large compared with the wavelength of light are derived. Taking into account the scattering of light in disperse adsorbent–adsorbate systems, these quantities are averaged over the direction of incidence and the polarization angle of the light. An absorption cross-section of adsorbed molecules analogous to the molar extinction coefficient of dissolved molecules is defined and its frequency dependence is discussed.