A simple theoretical approach of atom ionisation by ultra-intense and ultra-short laser pulses

A simple non-perturbative theory based on Coulomb-Volkov states can predict accurately angular and energy distributions of electrons which are ejected from atomic targets by ultra-intense and ultra-short laser pulses. The pre dictions are in very good agreement with 'exact' numerical calculations as long as the electric field has not enough time to oscillate. The agreement is all the better that the principal quantum number of the initial state is high. The power of the present approach is particularly apparent with very strong fields when the ponderomotive energy is above 1 KeV. Beyond this po int, full numerical treatments become very lengthy and finally do not conve rge whereas the present Coulomb-Volkov theory still makes reliable predicti ons in very short computer times.