Eur. Phys. J. D 26, 7-13 (2003)
https://doi.org/10.1140/epjd/e2003-00063-3

Probing electron-electron correlation with attosecond pulses

¹ Laboratoire de Physique Atomique, Moléculaire et Optique, Université catholique de Louvain, 2 chemin du cyclotron, 1348 Louvain-la-Neuve, Belgium
² Katedra Fizyki Jądrowej i Bezpieczeństwa Radiacyjnego, Uniwesytet Łódzki, ul. Pomorska 149/153, 90-236 Łódź, Poland
³ Centre Lasers Intenses et Applications (UMR 5107 du CNRS) , Université de Bordeaux I, 351 cours de la Libération, 33405 Talence, France

Corresponding author: ^a Piraux@fyam.ucl.ac.be

Received: 13 November 2002
Revised: 17 January 2003
Published online: 18 March 2003

Abstract

We study two-photon double ionization of helium in its ground state at sufficiently low laser intensities so that three and more photon absorptions are negligible. In the regime where sequential ionization dominates, the two-photon double ionization one-electron energy spectrum exhibits a well defined double peak structure directly related to the electron-electron correlation in the ground state. We demonstrate that when helium is exposed to subfemtosecond or attosecond pulses, both peaks move and their displacement is a signature of the time needed by the He⁺ orbital to relax after the ejection of the first electron. This result rests on the numerical solution of the corresponding non-relativistic time-dependent Schrödinger equation.