Optical Constants of Metals in the Extreme Ultraviolet II Optical Constants of Aluminum, Magnesium, and Indium at Wavelengths Shorter than Their Critical Wavelengths*

Measurements of the index of refraction of Al, Mg, and In as a function of wavelength have been made from 300 Å to their critical wavelengths. The measurements, made on films evaporated onto glass substrates, were obtained by using a “critical-angle” technique. It was found that the index of refraction of Al and Mg in this wavelength range can be described to a good approximation by the free-electron theory of Drude, while that of In cannot. The extinction coefficient was calculated for Al and Mg on the basis of the free-electron theory and, in the case of Al, compared with measured values. The optical properties of Al over a wavelength range from 300 to 6000 Å are discussed and compared with results predicted by the free-electron theory.