Optical constants from mirror reflectivities measured at synchrotrons

Improved mirror reflectivity measurement techniques have been introduced to permit more accurate determinations of optical constants and 3 in the complex index of refraction n = 1-i3 over the energy range 50 to 5000 eV. When the density has been detennined by x-ray or other means, one can calculate the real and imaginary parts, I ' and I ", of the complex atomic scattering factor I = fo f ' if " from and 3. Preliminary results are given for the Ni Lifi edge around 852 eV, and the Au M edge region from 2150 to 3500 eV. Since these are the first experimental evaluations of for these element edges, they are compared with appropriate reservations to semi-empirical tabulations. There is much potential for this technique applied to synchrotron sources.