Ultrafast strong field physics

Ultrafast dynamics is an exciting aspect of modern quantum physics. It allows one to get direct access to the fastest motion inside and in between atoms and molecules that constitute the matter that is surrounding us, where the coherence times can be as short as femtoseconds (10^-15 s) or even attoseconds (10^-18 s). Strong laser fields are available as pulsed flashed of light, with durations of only a few optical oscillation cycles in the few-femtosecond regime, and an electric field strength that becomes comparable to the electromagnetic binding forces within atoms and molecules. These pulses are a pivotal tool of light-matter interaction, to measure, understand and control the dynamics of atoms and molecules at the fundamental level. Combining them with new attosecond light sources at extreme ultraviolet and x-ray wavelength, derived from high-order harmonic generation or at (x-ray) free-electron laser facilities, reveal dynamic fingerprints that are very specific for each atomic species (i.e., time-resolved ultrafast x-ray spectroscopy).

In this lecture I will give a basic introduction into the fascinating physics of ultrafast light-matter interaction with strong laser fields. We will discuss the relevant tools needed for this type of research, how attosecond pulses can be produced in a laser laboratory, and how ultrashort intense x-rays can be produced with free-electron lasers at facilities like FLASH/DESY or European XFEL. We will place particular emphasis on the ultrafast absorption response of atoms and molecules, how absorption spectra develop on the femtosecond timescale, and learn how strong fields can be utilized to control them. We often use the helium atom as a natural platform for an entangled quantum system with its two active electrons, which allows us to learn more about Fano resonances and femtosecond autoionization dynamics. We will also discuss very new findings such as how a population inversion of this correlated two-electron system can be achieved with femtosecond pulses from a free-electron laser.

• This weekly 2-hr lecture will take place each Tuesday afternoon (16h-18h, starting time 16:15h), with the first lecture given on 21.04.2020.
• The lecture and discussions will be given online through “Zoom”.
• The link to the meeting will be distributed through email before the lecture.

Homepage of our research group:

https://www.mpi-hd.mpg.de/mpi/en/research/scientific-divisions-and-groups/quantum-dynamicscontrol/research/excited-atomsmolecules-in-strong-fields-ag-ott