Attosecond dynamics of electron correlation in doubly excited atomic states

Abstract

We have solved the time-dependent Schrödinger equation describing the simultaneous interaction of the He 1s2s 1S state with two laser-generated pulses of trapezoidal or Gaussian shape, of duration 86 fs and of frequencies ω1 = 1.453 au and ω2 = 1.781 au. The system is excited to the energy region of two strongly correlated doubly excited states, chosen for this study according to specific criteria. It is demonstrated quantitatively that, provided one focuses on the dynamics occurring within the attosecond timescale, the corresponding orbital configurations, 2s2p and 2p3d 1Po, exist as nonstationary states, with occupation probabilities that are oscillating as the states decay exponentially into the 1sεp continuum, during and after the laser-atom interaction. It follows that it is feasible to probe by attosecond pulses the motion of configurations of electrons as they correlate via the total Hamiltonian. For the particular system studied here, the probe pulses could register the oscillating doubly excited configurations by de-exciting to the He 1s3d 1D state, which emits at 6680 Å.

Watching the emergence of a Fano resonance in doubly excited helium

“…Nevertheless, our experiments capture the essential buildup of the Fano resonance despite the currently limited delay range. Our measurements are compared with numerical calculations and an analytic theory of Fano resonances in order to analyze and confirm the experimental observations [1]. Therefore, we solved the full 3D twoelectron Schrödinger equation from first principles using the time-dependent close-coupling method [14,15].…”

“…Among the most well-known examples are the resonances in the extreme ultraviolet (XUV) absorption spectrum of doubly excited helium. From the early works on attosecond dynamics in helium [1,2] until today, there has been substantial theoretical interest on how these spectral lines emerge and evolve after the transition is triggered and the subsequent process of autoionization takes place [3][4][5][6][7][8][9], also in the presence of strong near-infrared (NIR) laser fields.…”

Pump and probe ultrafast electron dynamics in LiH: a computational study

“…It is shown that even at the high powers required to pump a sizeable fraction of molecules it is possible to maintain tight control over the dynamics of the electrons. Other recent studies of ultrafast processes include the work on localization of electrons by the laser pulse [46]- [48], on LiCN [49], on inducing ring currents [50,51], on the importance of correlation effects in charge migration [52]- [54] and on other intense field effects on molecules [55]- [66]. We pay special attention to the control of the electron dynamics that is allowed by the physical parameters of the pump and to the probing of the resulting coherent motion.…”

Nonperturbative computation of the time-resolved formation of the profile of autoionizing states as a function of the intensity and duration of ultrashort pulses

“…In 2002, soon after the announcement of the production of single pulses of ultrashort duration in the scale of attoseconds (as) [6], we reported the results and analysis of an ab initio, electronic structure-dependent nonperturbative calculation, which involved the time-resolved effects at the attosecond scale of strong electron-pair correlations [7,8]. Specifically, by including in the Hamiltonian two simultaneous and short excitation pulses, we computed the time-resolved preparation and autoionization of low-lying 1 P o doubly excited resonance states of He, the corresponding amplitudes of the electron correlation beats, and the time-resolved rearrangement of pairs of electrons into different geometrical locations [7,8].…”

“…In this way, the choice of the problems in [7,8] and their quantitative solution in terms of the SSEA demonstrated from the point of view of theory a possible domain of useful applications of spectroscopy at the attosecond scale, namely, the probing of electron correlations in strongly correlated systems and of the interplay between electronic structure and electron dynamics.…”