Extracting generalized multiphoton ionization cross-sections from nonperturbative time-dependent calculations: An application in positronium
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748
2 Foundation for Research and Technology Hellas, Institute of Electronic Structure and laser, P.O. Box 1527, Heraklion 71110 Crete, Greece
Published online: 15 April 2000
Ab initio time-dependent (TD) calculations of the behavior of positronium (Ps) under strong subpicosecond laser pulses are presented. The results are compared with results in H through scaling. It is found that a substantial amount of the population can be found in excited states after the pulse. In the perturbative regime, generalized multiphoton ionization cross-sections are extracted from the results of the time-dependent calculations. The generalized cross-sections are used to predict the response of Ps to nanosecond laser pulses at wavelengths of current experimental interest. Beyond the application to Ps, the generality of the method for extracting generalized cross-sections from TD nonperturbative calculations is discussed.
PACS: 32.80.Rm – Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) / 32.80.-t – Photon interactions with atoms / 36.10.Dr – Positronium, muonium, muonic atoms and molecules
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000