Excitation and ionization of sodium clusters by a strong electromagnetic field

This paper reports on a study of the excitation and ionization of small sodium clusters by femtosecond light pulses with a maximum intensity of 5×10¹²–1×10¹⁴ W/cm² and photon energy from 1 to 3 eV made in terms of the density functional theory and jellium model through direct numerical solution of the Kohn-Sham time-dependent equation. The dependence of the degree of ionization on the intensity, duration, and frequency of the light pulses, as well as on the cluster size, is studied. The efficiency of the processes is shown to be determined primarily by the field intensity rather than by the total pulse energy.