报告题目：Mapping Electron Dynamics in Gaseous and Condensed Matter Using Tailored Ultrafast Tabletop X-ray Sources

报 告 人：王鹤，Lawrence Berkeley National Laboratory，USA

报告时间：12月27日11:00

报告地点：理科楼B315

报告摘要：In the microscopic world, the timescale of electron motion ranges from a few hundred attoseconds (10-18 s) to several femtoseconds (10-15 s), and is driven by electron-electron and electron-nuclear correlations. Previously, static measurements mainly provided time averaged information in the spectral domain, without shedding new light on the temporal dynamics of electrons and their correlation with other degrees of freedom in complex systems. This restricts our understanding and control of intermediate steps in chemical reactions and phase transitions. In my presentation, two examples will show that electron dynamics can now be observed and controlled in the time domain via novel ultrafast X-ray sources. In the first example, we combined isolated attosecond XUV pulses generated from the double optical gating (DOG) technique with a few-cycle NIR dressing field to control the electron autoionization process in argon [1, 2]. This experiment demonstrates the possibilities of controlling chemical reactions using strong laser fields. In the second example, angular resolved photoemission spectroscopy (ARPES) was integrated with single harmonic XUV sources. By using a UV laser as the driving field, we were able to generate a high flux (1013 photon/s) single harmonic source with a narrow band (<50 mev), and a high repetition rate (50 khz) without using a complicated monochromator [3]. through nir-pump/xuv-probe spectroscopy, complex degrees of freedom, such as electron-phonon and electron-electron correlations, can be accessed directly in the time domain, which provides insight into the properties of strongly correlated materials such as high tc superconductors. these techniques offer new paths to observing and controlling electron dynamics in complex systems.

[1] X. Feng, et al., Phys. Rev. Lett., 103, 183901 (2009)

[2] H. Wang, et al., Phys. Rev. Lett., 105, 143002 (2010)

[3] H. Wang, et al., Conference on Lasers and Electro-Optics (CLEO), QF1C2, San Jose, CA (2013)