OPTICAL-CONSTANTS OF AMORPHOUS-CARBON IN THE MID-IR (2.5-25 MU-M, 4000-400 CM(-1))

Laboratory measurement of the Fresnel reflectance are used to derive t he real and imaginary indices of refraction of amorphous carbon in the 2.5-25 mu m region. Comparison to previously reported optical constan ts, derived from extinction measurements at these wavelengths, show bo th similarities and differences. The differences are likely due to the different samples studied. wavelength-dependent calculated extinction coefficients (Q(ext)/a) from these values derived here are intermedia te in value to previously reported Q(ext)/a other amorphous carbon sam ples. The overall spectral shape exhibits a lambda(-a) behavior with a lpha = 1.05 +/- 0.05. However, more spectral structure is seem in the 18-25 mu m region than has been reported previously.