Electron Shell Ionization of Atoms with Classical, Relativistic Scattering

Abstract

We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of 2 × 10(19) W/cm(2). Comparisons between the gases reveal the energy of the outgoing photoelectron determines its momentum, which can be scattered as far forward as 45° from the laser wave vector k(laser) for energies greater than 1 MeV. The shell structure in the atom manifests itself as modulations in the photoelectron yield and the width of the angular distributions. We arrive at an agreement with theory by using an independent electron model for the atom, a dipole approximation for the bound state interaction, and a relativistic, three-dimensional, classical radiation field including the laser magnetic field. The studies provide the atomic physics within plasmas, radiation, and particle acceleration in ultrastrong fields.

Photoelectron energy spectra from elastic rescattering in ultrastrong laser fields: A relativistic extension of the three-step model

“…Ionization and propagation components of this model compare favorably with recent ultrastrong field experiments [17]. Monte Carlo trajectory ensembles in the model capture essential quantum aspects of the electron [23,24] and such semiclassical approaches have been compared to full quantum solutions with the Dirac equation [29].…”

“…Relativistic dynamics and a focal geometry inherent to all ultrastrong field experiments lead to complicated field accelerations that depend on the position and time in the laser field. Rendering a result for comparison to experimental result has involved, for example [17], integration over 10~3-m distances and 10~13 s. There is also a natural extension of the technique to plasma physics in ultrastrong fields, which utilizes classical particle-in-cell methods.…”

“…5 Fig. 5(d) has been modeled using the experimental focus, spatial volume, energy resolution, angular acceptance [17,41], and multiple charge state distribution expected as ionization proceeds from neutral Xe to Xe26+ by the end of the pulse. Comparing the data with our calculation, one can see that the high-energy rescattering expected nonrelativistically is absent.…”

“…laser fields (2 x 1019 W /cm 2) [17]. In these ultra strong fields, relativistic dynamics [18] are important and photoelectron energies can exceed several times the electron rest mass [19].…”

Limits of Strong Field Rescattering in the Relativistic Regime

“…For ultrahigh intensities (Γ R 1), the Lorentz deflection is very large and there is no observed interaction between the photoelectron and parent ion [39,40].…”