| 1. |
- Pop, Mihai, et al.
(författare)
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Single-shot transverse coherence in seeded and unseeded free-electron lasers: A comparison
- 2022
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Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 25:040701
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Tidskriftsartikel (refereegranskat)abstract
- The advent of x-ray free-electron lasers (FELs) drastically enhanced the capabilities of several analytical techniques, for which the degree of transverse (spatial) coherence of the source is essential. FELs can be operated in self-amplified spontaneous emission (SASE) or seeded configurations, which rely on a qualitatively different initialization of the amplification process leading to light emission. The degree of transverse coherence of SASE and seeded FELs has been characterized in the past, both experimentally and theoretically. However, a direct experimental comparison between the two regimes in similar operating conditions is missing, as well as an accurate study of the sensitivity of transverse coherence to key working parameters. In this paper, we carry out such a comparison, focusing in particular on the evolution of coherence during the light amplification process.
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| 2. |
- Uhl, D., et al.
(författare)
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Extreme Ultraviolet Wave Packet Interferometry of the Autoionizing HeNe Dimer
- 2022
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 13:36, s. 8470-8476
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Tidskriftsartikel (refereegranskat)abstract
- Femtosecond extreme ultraviolet wave packet interferometry (XUV-WPI) was applied to study resonant interatomic Coulombic decay (ICD) in the HeNe dimer. The high demands on phase stability and sensitivity for vibronic XUV-WPI of molecular-beam targets are met using an XUV phase-cycling scheme. The detected quantum interferences exhibit vibronic dephasing and rephasing signatures along with an ultrafast decoherence assigned to the ICD process. A Fourier analysis reveals the molecular absorption spectrum with high resolution. The demonstrated experiment shows a promising route for the real-time analysis of ultrafast ICD processes with both high temporal and high spectral resolution. © 2022 American Chemical Society.
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| 3. |
- Zitnik, M., et al.
(författare)
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Interference of two-photon transitions induced by XUV light
- 2022
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Ingår i: Optica. - : Optica Publishing Group. - 2334-2536. ; 9:7, s. 692-700
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Tidskriftsartikel (refereegranskat)abstract
- The relative phase of first (omega(1)) and third harmonics (omega(3)) extreme ultraviolet light pulses was varied to control the population of the 2s(2) state in helium through the interference of omega(1) + omega(1) and omega(3) - omega(1) two-photon excitation paths. The population was monitored by observing the total electron yield due to the 2s(2) autoionization decay. Maximum yield occurs when the relative phase of the two harmonics matches the phase difference of complex atomic amplitudes governing the two excitation paths. The calculated trend of atomic phase differences agrees well with the measured data in the spectral region of the resonance, provided that time-reversed -omega(1) + omega(3) path is also taken into account. These results open the way to accessing phase differences of two-photon ionization paths involving energetically distant intermediate states and to perform interferometry in the extreme ultraviolet range by monitoring final state populations. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
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