Published online by Cambridge University Press: 14 August 2015
The reflectance of aluminium films has been determined with films free of contaminating layers (Feuerbacher and Steinmann, 1969.) It has been shown that the reflectance of smooth aluminium films is 91% at the Lyα line. The influence of the surface plasmon excitation has also been investigated. This shows up as a dip in the reflectance if the film is not perfectly smooth. It imposes stringent requirements on the polishing of mirror substrates if optimum reflectance is required in the 1200–1700 Å region, since the influence of the surface plasmon is caused by surface roughness of lateral dimensions less than 1000 Å.