Nonsequential double ionization: a quasiclassical analysis of the Keldysh-type transition amplitude

The S-matrix amplitude of nonsequential double ionization, written down in the Volkov state basis, has been calculated by a saddle-point method. The distribution in the total and relative momenta of the two emitted electrons is given in analytical form. The result obtained is discussed in the context of the recently measured differential momentum distributions in argon. (C) 2001 Optical Society of America.