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SYSX: Symposium Soft X-ray induced ultafast processes on the atomic scale

SYSX 2: Soft X-ray induced ultrafast processes II

SYSX 2.1: Hauptvortrag

Donnerstag, 22. März 2007, 16:30–17:00, 6G

Atomic photoionization by femtosecond soft X-ray pulses — •Mathias Richter¹, Sergey V. Bobashev², Andrei A. Sorokin^1,2, Kai Tiedtke³, Hubertus Wabnitz³, and Michael Wellhöfer⁴ — ¹Physikalisch-Technische Bundesanstalt, PTB, Abbestraße 2-12, D-10587 Berlin, Germany — ²Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia — ³Deutsches Elektronen-Synchrotron, DESY, Notkestraße 85, D-22603 Hamburg, Germany — ⁴Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

The contribution refers to recent results on atomic photoionization obtained in focused photon beams at the new free-electron laser (FEL) in Hamburg (FLASH) by ion time-of-flight mass/charge spectroscopy. The experiments were performed with emphasis on a quantitative determination of pulse energy in the order of 10 microjoule and focus diameter down to 3 micrometer which yields, together with the estimated pulse duration of 10 to 30 fs, irradiance levels of up to 1e16 W/cm2 achieved. Strong non-linear behavior due to multi-photon processes was observed on helium, neon, and xenon atoms studied as a function of photon intensity. Results are discussed with regard to the role of sequential and direct multi-photon ionization and a theoretical description by perturbative and non-perturbative methods.