Recorded with a two-crystal vacuum spectrometer, the absorption curve for argon gas near the $K$ absorption edge, 3866 x.u., is analyzed in terms of the main edge and the $1S\to \mathrm{nP} \mathrm{}(n>\mathrm{}3\mathrm{})\mathrm{}$ series of resonance absorption lines. The main edge is determined uniquely as follows: the wave-length position is taken as at the series limit; the width is obtained from the measured width of the most intense absorption line; and the shape is given by the theoretical arctangent curve. The wave-length positions of all the resonance absorption lines are taken from the optical terms of potassium, and, with the width and shape of each line known, the various members of the series $1S\to \mathrm{nP}$ are determined uniquely. The relative intensities of these lines are 100: 34: 18: 8.5, etc. This analysis illustrates the type and completeness of the analysis we should like to make for solid absorbers, but, unfortunately, the definition and meaning of the main edge of a solid absorber are rather obscure.

• Received 23 June 1939

DOI:https://doi.org/10.1103/PhysRev.56.295