Multiple Excitation and Ionization of Inner Atomic Shells by X Rays

Reinvestigation of the region of the argon $K$ absorption edge has revealed a new resonance absorption structure followed by a new continuum. These new features may be interpreted as arising from double-electron-excitation processes involving an $M$ electron as well as the $K$ electron. The first new resonance line lies about 22 eV above the first line in the previously observed single-electron-excitation resonance structure. No additional resonance structure was found in the region from zero to about 50 eV.