The K Absorption Edges of Potassium and Chlorine in Various Compounds

The $K$ absorption edges of potassium and of chlorine were photographed by means of a vacuum spectrometer of the type designed by Siegbahn. Four compounds were used for the absorption of potassium; namely, sylvine, orthoclase, lepidomelane, and phlogopite. In the first two, the absorption occurred in the reflecting crystal itself; in the last two, in thin sheets of the substance placed in the path of the beam which was dispersed by a calcite crystal. The chlorine of the sylvine also gave an excellent Cl $K$ absorption edge. In these photographs as many as five secondary edges were observed. The fine structure of the potassium edge thus extended in wave-lengths from 3429 to 3365 x.u, or over a range of about 67 volts. The fine structure of the chlorine edge extended from $\lambda =4383\mathrm{}$ x.u. to $\lambda =4341\mathrm{}$ x.u., or about 27 volts. That portion of the fine structure which is more remote from the principal edge is not satisfactorily explained by Kossel's original hypothesis, and is perhaps best accounted for by double ionization of the atoms absorbing the x-radiation.