Non-Sequential Double Ionization of atoms by strong laser fields is very complicated, but is amenable to classical description.We will review our three-dimensional classical-ensemble studies of double ionization, and show the semi-quantitative agreement with experimental results.We find that the double ionization typically proceeds through a sequence of events–single ionization followed by recollision excitation, with over-the-barrier ionization occuring a portion of a laser cycle later.We consider laser wavelengths 780 nm and 390 nm.
*work supported by the National Science Foundation under Grant No.~0355035 and 0653526 to Calvin College