הנדסת חשמל - סמינר - ד"ר אבנר פליישר

~~You are invited to attend a lecture
By

Dr. Avner Fleischer
Department of Physics and Optical Engineering, ORT Braude College, P.O. Box 78, Karmiel 21982, Israel
Solid State Institute and Physics Department, Technion-Israel Institute of Technology, Haifa 32000, Israel.
 
Filming an electron as it flows inside an atom using a time-resolved laser STM (Scanning Tunneling Microscope)
Atoms and Molecules subjected to intense infrared laser fields may ionize by one of the most fundamental quantum processes: tunnel ionization. Depending on the release time of the electron into the continuum, one of two scenarios might take place. In the first, the electron simply flies towards the detector. I will show that this electron carries significant fingerprints of the electronic orbital from which it was torn. By analyzing its properties (momentum, energy) in a COLTRIM (cold target recoil ion momentum) spectrometer, we essentially constructed a "laser-STM" – an analogue to the conventional STM - capable of studying electron dynamics with ultrafast temporal resolution. I will show how this machinery can be used to take femtosecond-resolution snapshots of  an evolving electronic wavepacket density inside several atoms and molecules [1]. This work paves the way towards imaging of more complex electronic processes, such as charge transfer in molecules and semiconductor devices. In the second scenario the electron might return to the vicinity of the ion and recollide with it-  giving rise to the emission of high energy photons by high harmonic generation (HHG). I will present our recent solution to a problem which existed nearly 20 years in the field of HHG: how does one control the polarization state of the emitted harmonics [2].
[1]  A. Fleischer, H. J. Wӧrner, L. Arissian, L. Liu, M. Meckel, A. Rippert, R. Dӧrner, D. M. Villeneuve, P. B. Corkum and A. Staudte, "Probing Angular Correlations In Sequential Double Ionization", Phys. Rev. Lett. 107 113003 (2011).
 
[2] A. Fleischer, O. Kfir, T. Diskin, P. Sidorenko and O. Cohen,"Spin angular momentum and tunable polarization in high-harmonic generation", Nature Photonics 8 543 (2014).