Characteristic X-Rays from Metals in the Extreme Ultraviolet

Soft x-ray bands in region 50-500A from Li, Be, C, Na, Mg, Al, Si and Ba targets. A 2-meter grazing-incidence spectrograph was used. The bands (except those for Ba) correspond to transitions of outer (or conduction) electrons into a vacant $K$- or $L$-shell. The diffuseness of the bands is associated with the energy spread of the filled conduction electron levels. The Ba band is an $O\to N$ transition. The other metal bands extend over a fairly wide wave-length region and each has a sharp short wave-length edge which corresponds to the sharp "surface" of the filled conduction electron levels. The bands of C and Si have a more diffuse head which is connected with their semiconducting property. The energy spread of the metal bands may be calculated approximately from the Sommerfeld theory of metals; this provides a method of determining uniquely the number of conduction-electrons per atom in a metal. But the explanation of the precise shapes of the bands will require a more detailed theory and in particular an investigation of the transition probability of a conduction electron into a $K$- or $L$-shell. Some discussion is added on the absolute energies involved in the transitions which give rise to the bands.