Frequency-dependent optical constants of water ice obtained directly from aerosol extinction spectra

Abstract

We report here a new approach for determining frequency-dependent real and imaginary components of the refractive index of crystalline solids directly from the observation of the infrared spectra of the corresponding aerosols. The interplay between scattering and absorption observed in large (> 0.5-pm-radius) particles allows us to properly scale the imaginary component, determined from the absorption spectrum of small (around 0.3-pm-radius) aerosols, using calculations based on the Mie scattering theory. Once the imaginary indices are properly scaled, the corresponding real indices are determined through a Kramers-Kronig analysis. The method is applied to the study of water ice aerosols, and comparisons with previous measurements confirm that the method is sound and accurate, Reported here is a detailed study of the temperature dependence of the refractive index of ice. Experiments are reported over the temperature range from 130 to 210 K, which includes the region of interest for the study of polar stratospheric clouds (PSC's).

Film Growth of Ice by Vapor Deposition at 128−185 K Studied by Fourier Transform Infrared Reflection−Absorption Spectroscopy: Evolution of the OH Stretch and the Dangling Bond with Film Thickness

“…Simulated spectra of the OH stretch region (3800-2800 cm -1 ) based on the Fresnel reflection and Mie scattering theories with the appropriate optical constants obtained from the literature 36,38,46 are found to give good agreement with the experimental spectra. The intricate nature of the film growth process of ice at different temperatures can be qualitatively characterized as pc-ice or nc-ice, with their respective structures and properties (such as film thickness).…”

Infrared spectroscopy of sulfuric acid/water aerosols: Freezing characteristics

“…Sulfuric acid/water aerosols were studied in a lowtemperature flow cell that was previously used to study water ice [Clapp et al, 1995]. Briefly, the flow cell (pictured in Figure 1) has four separate, independently controlled cooling regions in which aerosols can be created and observed.…”

“…Detailed discussions of the methods used to form and observe cryogenic aerosols using infrared spectroscopy can be found elsewhere [Dunder et al, 1993;Dunder and Miller, 1990;Clapp and Miller, 1993;Clapp et al, 1995]. Aerosols are easily created by the rapid supersaturation of a gas mixture which results in the homogeneous nucleation of particles.…”

Retrieval of volcanic ash and ice cloud physical properties together with gas concentration from IASI measurements using the AVL model

“…The cloud altitude and v eff were as suggested in [8]. The refractive indices for the ice cloud were those of water ice determined in [9] for 210 K.…”