7 October 2024
James P. Cryan (SLAC National Accelerator Laboratory)
Attosecond spectroscopy at LCLS
The ultrafast motion of electrons is a frontier problem for photochemical processes, furthermore electron motion is a key ingredient of all chemical reactions. Electronic rearrangement is also the means by which light energy is harnessed in photochemistry. The timescale for coherent electron dynamics is set by the energetic splitting of the electronic states, which in small molecular systems, is on the scale of an electron volt (eV). This sets the natural timescale for electronic motion to be few-to-sub femtosecond (fs).
The study of these fundamental phenomena requires state-of-the-art light sources, such as X-ray free electron laser (XFEL) facilities, which produces high-brightness, ultrashort pulses, with wavelength continuously tunable across the x-ray regime. Schemes to provide isolated, sub-femtosecond pulses from an FEL are being explored at facilities world-wide, and recently we have demonstrated such pulses at the LCLS; opening the door for time-resolved measurements of ultrafast electron dynamics on their natural timescale. In my talk I will highlight our recent developments in producing and diagnosing attosecond scale soft x-ray pulse. I will go on to describe how we have employed these pulses to study ultrafast charge dynamics in both core-excited and low-lying cationic systems. Exploiting the interaction between strong-laser fields and the Auger-Meitner emission from core-excited systems we can probe electronic coherence. I will also show our first results on attosecond pump/probe experiments of ultrafast charge dynamics following valence ionization by attosecond x-ray pulse.
