Optical constants of organic tholins produced in a simulated Titanian atmosphere - From soft X-ray to microwave frequencies

The determination of the real (n) and imaginary (k) parts of the complex refractive index of thin films of the dark reddish organic solids called tholins, produced by continuous D.C. discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mb, is reported. For the 250 A-1000 micron wavelength range, n and k have been determined from a combination of transmittance, specular reflectance, interferometric, Brewster angle, and ellipsometric polarization measurements. Experimental uncertainties are estimated at + or -0.05 for n and + or -30 percent for k. The results in the visible range are consistent with deductions made by ground-based and spacecraft observations of Titan, in whose atmosphase tholins are thought to be present.