Excitation and ionisation of atoms by ultrashort pulses

It has been shown that while examining excitation and ionisation of Rydberg atoms by ultrashort lasers (10-15 sec) it is necessary to use the approximation of sudden excitations. The possibilities of excitation and ionisation of hydrogen atom and negative hydrogen ion, and also a full spectrum of scattering by an atom of ultrashort laser pulse are estimated. (author). 4 refs