Slope method for determining extinction coefficients*

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Abstract
A method is presented for obtaining the extinction coefficient, k, of an absorbing medium from critical-angle measurements. The maximum value of the slope of the reflectance vs angle of incidence curve is very sensitive to k and relatively insensitive to the refractive index, n, the polarization, P, and to surface imperfections. Theoretical curves are presented relating the magnitude of this maximum slope to k for constant values of n and P. In practice, the accuracy obtainable is limited by problems of normalization of the measured reflectance.