Allgemeines Physikalisches Kolloquium im Wintersemester 2008/2009

Ort:    48149 Münster, Wilhelm-Klemm-Str. 10, IG I, HS 2,
Zeit:    Donnerstag, 11.12.2008 16:00 Uhr c.t.
Kolloquiums-Kaffee ab 15:45 Uhr vor dem Hörsaal

Non-linear XUV processes with tabletop, sub-fs radiation sources
Prof. Dr. D. Charalambidis, Department of Physics, University of Crete and FORTH-IESL, Heraklion, Grichenland

Real time studies of several dynamic processes involving ultra-fast electronic motion in all states of matter require temporal precision of the scale of the atomic unit of time (24.1889 asec). Intensive efforts in ultra-short radiation pulse engineering led some years ago to the breakthrough into the attosecond regime, assuring in the dawn of attoscience. The early indications of attosecond localization in high harmonic generation have been followed up by a rapid evolution in the generation, characterization and applications of XUV attosecond pulses. Enormous progress has been made in shortening the XUV pulse duration to ~100asec and increasing the focused intensity to 10¹³-10¹⁴ W/cm², allowing the demonstration of a number of novel applications in different disciplines.
Attosecond pulse trains reached thus intensities high enough to induce non-linear processes based solely on XUV radiation. Utilizing such processes non-linear autocorrelation measurements have been successfully applied for the temporal characterization of the XUV waveforms. The same techniques open up the way to time resolved XUV applications.
Current efforts are focusing on merging two appealing and so far complementary features of asec pulses: “isolated” and “intense”. Towards this goal a highly promising ultra-fast harmonic generation switching method, based of what is called “polarization gating” has been recently successfully implemented.
The main limitation in further boosting the emitted XUV intensities is the depletion of the gaseous non-linear medium due to its ionization during the generation processes.  This obstacle can be surmounted through alternative generation approaches based on surface plasma harmonic emission. So far surface plasma harmonics have resulted a by an order of magnitude higher conversion efficiency than gas-harmonics and have been used in two-XUV-photon atomic ionization. However, theoretical predictions foresee photon numbers as high as 10¹⁶ per pulse and ultra relativistic focused intensities are highlighting the perspective of looking into a variety of new phenomena such as non-linear inner shell processes, non-linear relativistic effects, electron-electron correlations, non-destructive imaging of macromolecules et al
In my presentation, will review the developments summarized above.