Multielectron ionization processes in ultrastrong laser fields

The ionization of neon was studied in strong (10(14)-10(16) W/cm(2)) and ultrastrong (10(17)-10(18) W/cm(2)) laser fields. Measurements of ionization yields in ultrastrong fields reveal that they are dominated by sequential tunneling ionization of the ion charge states. The rescattering mechanism, identified with the generation of high-order harmonies and multiple electron ionization in strong fields, is modeled for ultrastrong fields and is shown to be reduced by orders of magnitude when compared with strong-field ionization. The results from the model are consistent with the experimental results and indicate that the reduced core size for ions and the Lorentz force in ultrastrong fields combine to reduce rescattering in ultrastrong fields. (C) 2003 Optical Society of America.