ABSOLUTE PHOTOABSORPTION MEASUREMENTS OF MG, AL, AND SI IN THE SOFT-X-RAY REGION BELOW THE L2,3 EDGES

Absolute measurements of the photoabsorption coefficient of Mg, Al, and Si from 25 eV up to the L3 absorption edge are presented. Transmission measurements were performed on free-standing thin films using a laser-produced plasma source. The surface oxide is corrected for by taking the ratio of the absorption for different film thicknesses. The values so obtained are, in general, lower than have been reported in the literature. Structure below the edge is observed for Al and Si. Despite the fact that the absorption below the L3 edge is due to the valence or conduction electrons, the magnitude of the absorption coefficient for the solid is much higher than is predicted by a simple Drude model and is close to that expected from calculations for the free atom.