Absorption by Aluminum in the Soft X-Ray Region

Measurements on the absorption by aluminum in the spectral range extending from 80A to 600A have been carried out by the use of a grazing incidence spectrograph. The investigation has revealed that the strong absorption band centered at 129A is a "surface" phenomenon which takes place in the metal-substrate interface of absorbers prepared by evaporation. Thin metallic foils without a substrate do not show this absorption band. The present data have yielded consistent results for the mass-absorption coefficient, whose value ranges from 1.0×${10}^4$ ${\mathrm{cm}}^2$/g to 2.8×${10}^4$ ${\mathrm{cm}}^2$/g in the above spectral region. As observed previously in connection with the $K$ edge, a secondary structure is also present on the short wavelength side of the $L_{2,3}$ edge. The $L_1$ absorption limit has not been detected.