Stimulated radiative recombination and x-ray generation

Abstract

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 ប X ϭE p ϩU p ϩ͉E B ͉ ϩ2ͱ2U p E p , with E p being the kinetic energy of the ingoing electron, U p the ponderomotive energy, and E B the binding energy. The equivalence of the two models for the zero-range interaction is also shown.

Resonant electron-atom bremsstrahlung in an intense laser field

“…Within this interval, the average value of the cross section σ µ depends weakly on µ , forming a plateau in the LARA or LARR spectrum [21][22][23]. Under the condition p > |e|F /ω, the lower ( …”

“…Refs. [21][22][23] for the LARR process) and corresponds to replacing the QES p i by the Volkov wave χ p i , i.e., neglecting the interaction of the active electron with the scattering potential. Numerical results for electron-proton BrS spectra in a laser field with λ = 400 nm (the second harmonic of a Ti:sapphire laser) and intensity I = 1.67 × 10 14 W/cm 2 are shown in Fig.…”

The time-dependent Schrodinger equation

“…The result obtained fits in the picture of a system of reference moving with the electron: the momentum is not modified by the field, but Volkov solutions acquire a timedependent phase during the interaction. [14,15,16]; at the same time many ways have been proposed to assess their accuracy and to improve them [17,18,19]. We will use them to describe the motion of the electron far from the ion, and it will be one of our major approximations.…”

Polarization and angular distribution of the radiation emitted in laser-assisted recombination

“…Slight modifications of this scheme have been considered in order to take into account, though approximately, the electron-ion interaction. In all the proposed treatments, the calculated emission spectra show a large plateau due to absorption of a large number of photons, followed by an abrupt cutoff [4,5,6]. …”

“…In the presence of intense monochromatic electromagnetic fields, the electron can exchange a large number of photons of the assisting radiation field and may recombine in a bound state [3,4,5] emitting x-rays whose frequency depends on the number of the exchanged laser photons, according to the energy conservation law:…”