Stimulated radiative recombination and x-ray generation

We consider the process of electron-ion recombination in a powerful laser field and investigate the spectrum of emitted x-ray radiation. This process is of interest in the interaction of laser radiation with gaseous or solid targets in connection with harmonic and coherent x-ray production. The process is treated in the framework of the inverse Keldysh-Faisal-Reiss model describing the ingoing electron either by a Gordon-Volkov wave or by a Coulomb-Volkov solution. Even for higher energies of the impinging electrons, considerable Coulomb effects are recognized. We evaluate the rates of the generated x-ray field and determine the energy range of its spectrum. The maximum photon energy achieved by this process is estimated by ωX=Eₚ+Uₚ+|EB|+2√2UₚEₚ, with Eₚ being the kinetic energy of the ingoing electron, Uₚ the ponderomotive energy, and EB the binding energy. The equivalence of the two models for the zero-range interaction is also shown.