Auger cascades in aluminum

Abstract

Transition-rate expressions are developed to analyze the Auger cascade leading to multiply charged ions following inner-shell vacancy production. In general, our aim is to predict the intensity and spectral distribution of the soft x-ray emission occurring at the termination of the Auger cascade, to determine when and if there can be an inner-shell population inversion, and at what pumping level one will obtain amplified spontaneous emission. Aluminum is examined in detail starting with an initial $K$-shell vacancy, and it is found that there can be significant amplified spontaneous emission in the 160-170-Å region providing one has a hard x-ray flux of about ${10}^{11}$ W/${\mathrm{cm}}^2$ at energies greater than the Al $K$-shell binding energy. It is hypothesized that the recent observations of Jaegle et al., indicating gain at 117.4 Å in a two-plasma experiment, can be accounted for via x-ray coupling between the plasmas. An experiment to check the hypothesis is advanced.