Optical constants of organic tholins produced in a simulated Titanian atmosphere: From soft x-ray to microwave frequencies
Abstract
As part of a continuing series of experiments on the production of dark reddish organic solids, called tholins, by irradiation of cosmically abundant reducing gases, the synthesis from a simulated Titanian atmosphere of a tholin with a visible reflection spectrum similar to that of the high altitude aerosols responsible for the albedo and reddish color of Titan has been reported (C. Sagan and B. N. Khare, 1981, Bull. Amer. Astron. Soc.13, 701; 1982 , Orig. Life. 12, 280) and [C. Sagan, B. N. Khare, and J. Lewis, in press. In Saturn (M. S. Matthews and T. Gehrels, Eds.), Univ. of Arizona Press, Tucson]. The determination of the real ( n) and imaginary ( k) parts of the complex refractive index of thin films of such tholin prepared by continuous D.C. discharge through a 0.9 N 2/0.1 CH 4 gas mixture at 0.2 mb are reported. For 250 Å ≤ γ ≤ 1000 μ m, n and k have been determined from a combination of transmittance, specular reflectance, interferometric, Brewster angle, and ellipsometric polarization measurements; experimental uncertainties in n are estimated to be ±0.5, and in k ± 30%. Values of n(≅1.65) and k (≅0.004 to 0.08) in the visible range are consistent with deductions made by ground-based and spacecraft observations of Titan. Maximum values of k (≅0.8) are near 1000 Å, and minimum values (≅4 × 10 -4) are near 1.5 μm. Many infrared absorption features are present in k( γ), including the 4.6-μm nitrile band.
- Publication:
-
Icarus
- Pub Date:
- October 1984
- DOI:
- 10.1016/0019-1035(84)90142-8
- Bibcode:
- 1984Icar...60..127K
- Keywords:
-
- Planetary Composition;
- Satellite Atmospheres;
- Titan;
- Environment Simulation;
- Gas Mixtures;
- Optical Properties;
- Organic Solids;
- Refractivity;
- Thin Films;
- SATURN;
- TITAN;
- SATELLITES;
- OPTICAL PROPERTIES;
- ORGANIC MATERIALS;
- X-RAYS;
- SIMULATIONS;
- ATMOSPHERE;
- MICROWAVES;
- FREQUENCIES;
- EXPERIMENTS;
- GASES;
- IRRADIATION;
- REFLECTANCE;
- SPECTRA;
- COMPARISONS;
- AEROSOLS;
- ALBEDO;
- COLOR;
- REFRACTIVE INDEX;
- INTERFEROMETRY;
- POLARIZATION;
- WAVELENGTHS;
- INFRARED;
- ABSORPTION;
- PROCEDURE