Quantum beats and fine structure in attosecond chronoscopy of strong-field photoionization of atoms

¹  Fock Institute of Physics, State University of Sankt Petersburg - Sankt Petersburg 198504, Russia
²  Donostia International Physics Center - E-20018 San Sebastian/Donostia, Basque Country, Spain, EU
³  Fakultät für Physik, Universität Bielefeld - D-33615 Bielefeld, Germany, EU
⁴  Institute of Nuclear Physics, Moscow State University - 119991 Moscow, Russia

Corresponding author: nkabach@mail.ru

Received: 20 December 2007
Accepted: 5 February 2008

Abstract

A theoretical model is presented which describes the time evolution of strong-field photoionization as studied in recent XUV pump-IR probe attosecond tunneling (attosecond chronoscopy) experiments. The excitation of intermediate weakly bound states by an ultra-short XUV pulse (pump) is described within a sudden approximation. The photoionization of these states by a delayed strong IR pulse (probe) is described by solving the non-stationary Schrödinger equation. The results of the calculations show that the coherence of the excited states plays an important role resulting in quantum beats when the XUV pulse precedes the IR pulse. For a large overlap of the pulses a pronounced fine structure in the cross-section is revealed. The calculations for Ne agree qualitatively with the experiment.