Charge states of many-electron atoms in a strong laser field

The nonresonant, multiphoton ionization of many-electron atoms is explained theoretically within the Thomas-Fermi model with the inclusion of an electromagnetic field. Numerical results are presented for the charge state and induced dipole moment versus the strength of the applied electric field, which, because of the scaling properties of the model, can be expressed as universal functions of the field. Our results compare favorably with those from recent ionization experiments performed on noble gases using laser fields.