IONIZATION OF A 2-ELECTRON ATOM IN A STRONG ELECTROMAGNETIC-FIELD

A one-dimensional model of a helium atom in an intense field of a femt osecond electromagnetic pulse has been constructed using the Hartree t echnique. ''Exact'' calculations have been compared to the approximati ons of ''frozen'' and ''passive'' electrons. A nonmonotonic dependence of the single-electron ionization probability on the radiation intens ity has been detected. Minima in the ionization probability are due to multiphoton resonances between different atomic states due to the dyn amic Stark effect. We suggest that the ionization suppression is due t o the interference stabilization in this case. (C) 1997 American Insti tute of Physics.