Speaker
Description
Attosecond pulse modes at XFELs, such as those employing slotted-spoiler devices, low bunch charge, or photocathode shaping, are increasingly available at facilities around the world [1-3]. The intensity and photon energy of attosecond XFEL pulses greatly exceed those of conventional attosecond HHG pulses, granting the potential to study a much wider range of systems and processes than have hitherto been accessible. With greater access to these ultrashort pulses comes a greater need for means to exploit and characterise them; applying the established methods of attosecond metrology at XFELs is not straightforward, due to inherent difficulties with timing and phase stabilisation.
In recent years we have developed, demonstrated, and refined novel techniques to realise attosecond pump-probe streaking spectroscopy at XFELs. These self-referencing methods make pairs of measurements, with each pair using different phases of the same probe laser pulse, which provides sufficient information to reconstruct the instantaneous field parameters [4, 5].
The latest experiments incorporate dual electron time-of-flight detectors positioned at different points along the beam’s axis of propagation, resulting in a consistent, measurable Gouy phase shift between the two measurements in each pair. Here, we present preliminary results from these experiments, in which we measured the few-femtosecond delay between carbon 1s photoemission and Auger-Meitner emission in CF$_4$ and CH$_4$ – thereby contributing a time-resolved experimental answer to a long-running theoretical debate regarding the effects of an atom’s chemical environment on its relaxation dynamics. This measurement, facilitated by our novel technique, would not be possible with conventional attosecond streaking apparatus, and heralds the wide range of future possibilities for time-resolved ultrafast science at XFELs.
References:
1. Huang, S. et al. Generating Single-Spike Hard X-Ray Pulses with Nonlinear Bunch Compression in Free-Electron Lasers. Phys. Rev. Lett. 119, (2017).
2. Duris, J. et al. Tunable isolated attosecond X-ray pulses with gigawatt peak power from a free-electron laser. Nat. Photonics 14, 30–36 (2019).
3. Zhang, Z. et al. Experimental demonstration of enhanced self-amplified spontaneous emission by photocathode temporal shaping and self-compression in a magnetic wiggler. New J. Phys. 22, 083030 (2020).
4. Haynes, D. C. et al. Clocking Auger electrons. Nat. Phys. 17, 512–518 (2021).
5. Haynes, D. C. Extending attosecond techniques to X-ray free-electron lasers. Doctoral dissertation, Universität Hamburg (2022).
| Scientific Topics | AMO Physics |
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