Two-Photon Ionization of He through a Superposition of Higher Harmonics
Nektarios A. PapadogiannisFoundation for Research and Technology-Hellas, Institute of Electronic Structure & Laser, P.O. Box 1527, GR-711 10 Heraklion (Crete), GreeceL. A. A. NikolopoulosFoundation for Research and Technology-Hellas, Institute of Electronic Structure & Laser, P.O. Box 1527, GR-711 10 Heraklion (Crete), GreeceD. CharalambidisFoundation for Research and Technology-Hellas, Institute of Electronic Structure & Laser, P.O. Box 1527, GR-711 10 Heraklion (Crete), GreeceG. D. TsakirisLaser Plasma Physics, Max Planck Institute of Quantum Optics, Max Planck SocietyP. TzallasLaser Plasma Physics, Max Planck Institute of Quantum Optics, Max Planck SocietyK. WitteLaser Plasma Physics, Max Planck Institute of Quantum Optics, Max Planck Society
2003en
ABI
Abstract
We present experimental results and theoretical analysis of two-photon ionization of He by a superposition of the 7th to the 13th harmonic of a Ti:sapphire laser. Solving the time-dependent Schr\"odinger equation for He in a coherent polychromatic field, the ${\mathrm{H}\mathrm{e}}^{+}$ yield is calculated. From this yield the number of ${\mathrm{H}\mathrm{e}}^{+}$ ions produced has been estimated and found in reasonable agreement with its measured value. The present results establish the feasibility of a second-order autocorrelation measurement of superposition of harmonics, and thus they represent the precursor towards the direct temporal characterization of attosecond pulse trains.
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