Attosecond Electronic Dynamics of the Valence States in Matter Measured with XFELs

Lead Research Organisation: Imperial College London
Department Name: Physics


A new era in ultrafast science began with the first demonstration in 2019 of attosecond duration single and two-colour pulses from an x-ray free-electron laser (XFEL). Enhanced Self Amplified Spontaneous Emission (eSASE), aka x-ray Laser Attosecond Pulses (XLEAP), was used to control the multi-GeV electron bunch before it enters the undulators so that it lased on a single high current peak to generate a transform limited x-ray pulse of a few hundred attoseconds duration. This landmark was achieved at the LCLS XFEL (Stanford Linear Accelerator Centre) with our team playing a strong role in this work from these early developments (published in Nature Photonics 2020). We soon used these pulses to carry out ground-breaking new scientific research, e.g. by making the first observation of a few-femtosecond quantum-beat in Auger-Meitner emission due to the formation of wave-packets (superpositions) of core excited electronic states (published in Science 2022).

The remarkable feature of XLEAP pulses is not only their very short duration of ~300 attoseconds, i.e. three hundredth millionth of a hundred millionth of a second, and x-ray wavelength (from 200 eV to 1500 eV photon energy), but that these pulses have tens of microjoule energy (containing about a million million x-ray photons) making them a billion times more intense than any alternative attosecond technology. This high brightness makes possible new concepts in ultrafast x-ray measurement. The high intensity and attosecond pulse duration are required for x-ray pump-probe measurements of electronic valence state dynamics and electronic Raman excitation that we will use to target new science in our proposed work.
We will focus on the ultrafast electronic dynamics in the valence/bonding states of matter through investigating: (a) attosecond timescale electronic dynamics in matter to capture the fundamental events of photoexcitation and how it can drive chemistry, (b) new types of electronic mediated x-ray non-linear interactions with the potential to uncover the full dynamics of electronic bonding in matter, and (c) the development of the theoretical capabilities to fully interpret the insights from these experiments. Together this research will make a step-change in ultrafast measurement capability and scientific understanding.

This research will open-up new ways to probe the dynamical events that control the fastest transformations in matter and will:
1/ Enable ultrafast measurement at unprecedented resolution (10^-16 s) in matter of all phases (i.e. gas, plasma, solid, liquid) using site and state specific probes
2/ Provide access to fleeting electronic quantum superposition states that lead to the phenomena of charge migration, and trace how electronic coherence is damped through coupling to the nuclear degrees of freedom (this is key to understanding x-ray radiation damage and charge directed chemical reactivity)
3/ Allow the role of interaction between an electronically excited molecule and its surroundings to be resolved and to track how photochemical and photophysical processes emerge in a condensed phase environment (this is key to the flow of energy and charge during matter transformation)
4/ Offer a new array of x-ray non-linear interactions capable of revealing the fundamentals of electronic coupling within matter (this is key to controlled quantum dynamics and measurement)
5/ Enhance the UK position as a world leader in ultrafast x-ray science and equip the nation with more skilled scientists to exploit future x-ray FEL opportunities
Description Bucksbaum Group - Stanford University 
Organisation Stanford University
Country United States 
Sector Academic/University 
PI Contribution We have provided ideas and expertise to progress research in ultrafast X-ray science by leading and participating in a number of joint beamtimes.
Collaborator Contribution Through this collaboration we have been able to efficiently engage in X-ray free electron laser research at the LCLS facility SLAC through their local resources and manpower. It has enabled around 10 separate beam-times.
Impact A number of research papers including 1 PRL, 2 Nature Communications and more in preparation.
Start Year 2011
Description SLAC Photon Sciences 
Organisation Stanford University
Department SLAC National Accelerator Laboratory
Country United States 
Sector Public 
PI Contribution We are a member of an international collaboration, the "Attosecond Campaign" coordinated by SLAC (Dr Agostino Marinelli and Dr James Cryan SLAC leads) aimed at developing attosecond measurements of electron dynamics using newly proven X-ray FEL capabilities.
Collaborator Contribution They provide the support of X-ray FEL beamtime and run the experimental endstation
Impact A papers published in PRL, Nature Photonics, Science
Start Year 2020
Description Theory collaboration with UAM group in Madrid 
Organisation Autonomous University of Madrid
Country Spain 
Sector Academic/University 
PI Contribution Collaboration with Prof Fernando Martin of UAM in planning experiments and analysis of data from earlier measurements in glycine. Collaboration with Prof Antonio Picon of UAM in providing data on impulsive stimulated Raman Stokes emission measured using an attosecond XFEL pulse in liquid water.
Collaborator Contribution Professor Martin is applying his RAS calculation methodology and treating nuclear dynamics in the problem of charge migration in glycine molecules. Prof Picon has developed a water dimer model to treat liquid water non-linear Raman response that now matches well the experimental results.
Impact Publications in preparation
Start Year 2023