Excitation and ionization of the hydrogen atom by intense femtosecond chirped laser pulses

摘要

The excitation and ionization processes of the hydrogen atom by intense femtosecond chirped laser pulses are investigated by solving numerically the three-dimensional time-dependent Schr?dinger equation. We study, in three distinct cases, the interaction of the atomic system with chirped pulses of different central carrier frequencies that correspond to some harmonics of a Ti-sapphire laser. We analyze, in each case, the mechanism of the population transfer from the ground to the excited electronic states and show how it differs depending on the sign of the chirp parameter. We also show that the ionization yield is sensitive to the chirp parameter when resonant or near-resonant transitions are induced by the chirped pulses. The latter are efficient to control the excitation process by inducing selective population transfer when compared with unchirped pulses.