L Dimou

STABILIZATION, ABOVE-THRESHOLD-IONIZATION AND DETACHMENT IN INTENSE ADIABATIC AND ULTRASHORT LASER PULSES

In this paper we treat by entirely ab initio methods, a number of phenomena in nonlinear dynamics in intense laser fields. In particular, we apply the recently developed Floquet-coupled-channel (FCC) method to investigate the phenomenon of adiabatic stabilization and formation of stabilization windows in hydrogen atom, as well as the frequency and intensity dependence of nonlinear-detachment process in hydrogen negative ion. Moreover, a solution is given, with examples, to the methodological problem of consistently evaluating the ATI-spectrum within the Floquet theory. Next, direct simulations are carried out to determine the influence of stabilization on the ATI-spectrum and on the bound state occupation probabilities of H-atom. Finally, the time-scale of formation of ATI-peaks is investigated and shown to be of the order of the rise-time of the pulse.

Differential cross sections of low-energy electron - hydrogen scattering in a laser field

Floquet close-coupling (FCC) analysis of stimulated electron - hydrogen scattering in the field of a low-frequency laser field is carried out. Results are obtained for one-, two- and three-photon absorption and emission processes in terms of the differential scattering cross sections as a function of the scattering angle. Two critical geometries are considered in which the argument of the Bessel function in the well known low-frequency formula becomes negligibly small. It is found that the ratios of the cross sections for small-angle scattering in both geometries are many orders of magnitude larger than predicted by the low-frequency formula (LFF). The result supports an analogous finding of many orders of magnitude larger values of the cross section measured in Ar and He by Wallbank and Holmes, and confirms the failure of LFF for small-angle scattering.

Line narrowing in a H atom in intense laser fields at sub-threshold and above-threshold frequencies

Abstract Line widths due to ionization decay of a H atom in intense laser fields are investigated by solving the (3+1)-D Schrodinger equation numerically exactly. Quantitative results for line narrowing both at sub-threshold and above-threshold frequencies are given and a mechanism for the appearance of minima in the line widths is discussed.

Reply to Comment on `Differential cross sections of low-energy electron-hydrogen scattering in a -laser field'

The long-range asymptotic behaviour of the interaction potential is of crucial significance for low-energy laser-assisted electron-atom scattering for emission/absorption of one or more photons, especially for the small scattering angles; this is not satisfied by the ansatz of the comment by Rabadan and co-workers, equation (9).

A Strongly Perturbed Quantum System: H-Atom in Intense Laser Field

The hydrogen atom provides one of the simplest real systems in nature which can be used to investigate the non-perturbative quantum dynamics in intense laser fields over a great range of the perturbation strengths. Such studies are useful in developing our intuitions about the behaviour of quantum systems in domains where the conventional ideas developed primarily from our knowledge of weak perturbations can no longer be used reliably. In the domain of strong perturbations new phenomena arise which are not observed otherwise.Recently significant progress has been made both experimentally and theoretically in this respect by studying the response of atoms in intense lasers. Prominent among the new effects observed are the so-called above threshold ionization or (ATI)1, above threshold detachment (ATD)2–4, and high harmonic generation5,6.