Interaction of intense short laser pulses with positronium

The ionization of the positronium is studied in the over-the-barrier regime. The Volkov and momentum-space strong-field approximation are applied to describe the ionization of the hydrogen-like atomic systems. Classical trajectory Monte Carlo calculations were also performed and a good agreement with quantum-mechanical calculations were found. The scaling of the ionization probability density as function of the reduced mass of the target is analyzed. We find that the maxima of the ionization probability density is determined by laser field parameters, and it's width can be characterised by the charge of the core and reduced mass of the target. (c) 2008 Elsevier B.V. All rights reserved.