The interaction of Li– with an ultrashort intense laser pulse is investigated by solving the time-dependent Schrödinger equation (TDSE) in the dipole approximation using a two-active electron approach. We describe the numerical solution of the TDSE and give a more detailed presentation of a technique for obtaining angular distributions for double ionization by intense ultrashort laser pulses. We show how selection rules observed in the angular distributions for double ionization by an intense laser field can be derived from the symmetry properties of the wave function. In an attempt to elucidate the mechanisms for double ionization in the multiphoton regime, we have performed numerical experiments for ionization by single cycle and double half-cycle pulses. Our preliminary results unveil the important contribution of the shake-off mechanism, in addition to the rescattering and sequential ionization mechanisms
