Classical Theory of High Field Atomic Ionization Using Elliptical   Polarization
  Important information about strong-field atomic or molecular ionization can be missed when using linearly polarized laser fields. The field strength at which an electron was ionized, or the time during a pulse of the ionization event are examples of such missing information. In treating single, double, and triple ionization events we show that information of this kind is made readily available by use of elliptical polarization. 
Xu Wang and J. H. Eberly
physics.atom-ph