Comment on `Feasibility of a hot-electron-pumped K-shell X-ray laser' by F.N. Chukhovskii et al., Opt. Commun. 154 (1998) 313-318

摘要

The main conclusion of the paper, `Feasibility of a hot-electron-pumped K-shell X-ray laser' by F.N. Chukhovskii et al, that an inversion on a Kα-transition can be generated by electron collisional ionization was shown to be in error. The authors did not take into account that the higher cross-section for L-hole generation will, under the conditions considered, invariably generate an absorption. For this reason, the gain on a Kα-transition must be written as GK = σK(NK-εNL)-μK, where σK is the cross-section for stimulated emission, NK and NL are the number densities of atoms with single K- and L-holes, and μK is the absorption coefficient of the laser material. The factor ε is the ratio of the statistical weights of the upper and lower levels.