Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

Abstract

An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.

Singularity in electron-core potential as a gateway to accurate multi-electron ionization spectra in strongly driven atoms

“…the delayed (e -, 2e -) one contributes the most to TI. This is consistent with soft potentials not accurately describing scattering of a recolliding electron from the core [23].…”

“…However, softening the Coulomb potential fails to accurately describe electron scattering from the core [23,24]. Indeed, the ratio of the scattering amplitude for the softcore potential over the one for the Coulomb potential decreases exponentially with increasing momentum transfer [23,24]. For recollisions [25], this implies that soft potentials are quite inaccurate for high energy recolliding electrons that backscatter.…”

“…The main premise in our model is that two interactions are most important during a recollision and hence are treated exactly. Motivated by the above mentioned studies [23,24,26,30,31], we account for the singularity in the Coulomb potential between each electron, bound or quasifree, and the core. Quasifree refers to a recolliding electron or an electron escaping to the continuum.…”

Intense VUV–xenon-cluster interaction revisited

“…that the potential-depth parameter has a large influence on the scattering cross section and thus the energy absorbed. However, it was found that the cross section saturates for large potential depths, but this value occurs at a potential depth that is typically larger than the ionization potential by an order of magnitude [22,29].…”