Electron shell ionization of atoms with classical, relativistic scattering
N. Ekanayake, S. Luo, P. D. Grugan, W. B. Crosby, A. D. Camilo, C. V. McCowan, R. Scalzi, A. Tramontozzi, L. E. Howard, S. J. Wells, C. Mancuso, T. Stanev, M. F. Decamp, and B. C. Walker
Accepted
We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of $2 \times 10^{19}$ 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$^{\circ}$ from the laser wavevector $k_{laser}$ 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 using an independent electron model for the atom, 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.