Multiple fragmentation of atoms in femtosecond laser pulses

Multiple ionization of atoms by an ultrashort intense laser pulse is a process in which the few-body problem is closely interrelated with the highly nonlinear interaction between the electrons and the external field. We review recent advances in unveiling the mechanisms behind the unusually large ion yields for double and multiple ionization observed in a strong laser pulse. Its study requires on one hand the combination of highly differential experimental techniques with laser systems having high repetition rates and on the other the development of new theoretical methods to simultaneously account for the long ranged Coulomb interaction between the particles and the field nonlinearity. Different mechanisms are analysed diagrammatically and quantitatively in comparison with experimental data for the total ion yields. Distributions for the electron and ion momenta of coincidence measurements are discussed along with predictions of the various theoretical methods.