TheKX-Ray Absorption Edge of Silicon

The $K$ absorption edge of silicon was measured in silicon metal and in the following compounds: quartz, sodium silicate, muscovite, biotite, phlogopite, lepidolite, carborundum, and an organic compound, mono ethyl siloxane. It was found that the quartz, sodium silicate, and the four micas all gave approximately the same wave-length for the absorption edge, namely, about 6700 x.u., while for the siloxane the value was 6706 x.u., and for the silicon metal and for carborundum it rose as high as 6718 x.u. It is to be noted that the surroundings of the silicon atom are the same for all those compounds which gave an edge at 6700 x.u. In the organic compound one oxygen has probably been replaced by the group ${\mathrm{C}}_2$ ${\mathrm{H}}_5$, while for carborundum and for silicon metal all four oxygens of the tetrahedral group surrounding the silicon atom have been replaced by carbon and by silicon, respectively.