Speaker
Description
Ultrafast imaging enables the investigation of nanoscale dynamics in single particles using individual X-ray pulses. Accurate interpretation of such images requires understanding the strong interaction between the X-ray pulse and the sample, particularly when the electronic structure effects is of interest.
We investigate ultrafast X-ray--induced dynamics in sodium iodide (NaI) nanoparticles using resonant single-particle imaging with ultrashort X-ray free-electron laser pulses at the SwissFEL Maloja endstation. Photon-energy scans across the I 3d absorption edge were recorded to probe the pulse-length-dependent scattering response. Single-particle diffraction patterns were reconstructed by phase retrieval to extract scattering intensity and particle size.
The measured scattering signals exhibit pronounced resonant features, with attosecond pulses providing a response closest to the ground-state electronic structure. For few-femtosecond pulses, the diffraction response is significantly modified, indicating the increasing influence of transient electronic excitations. Electronic structure simulations are employed to model X-ray--atom interactions and transient population dynamics, yielding time-dependent scattering cross sections. This combined approach provides insight into transient electronic configurations and defines the conditions under which ground-state resonant imaging can be achieved with attosecond XFEL pulses.
Funding Agency
We acknowledge support from the Swiss National Science Foundation under grant number 197372 and the Paul Scherrer Institute for provision of SwissFEL beamtime at the Maloja endstation.
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