The Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source

Ferguson, Ken; Bucher, Maximilian; Bozek, John D.; Carron, S.; Castagna, Jean-Charles; Coffee, Ryan; Curiel, G. Ivan; Holmes, Michael; Krzywiński, J.; Messerschmidt, Marc; Minitti, Michael P.; Mitra, A.; Moeller, Stefan; Noonan, Peter; Osipov, T.; Schorb, Sebastian; Swiggers, Michele; Wallace, A.; Yin, Junjie; Bostedt, Christoph

doi:10.1107/s1600577515004646

Cited by 68 publications

(53 citation statements)

References 26 publications

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“…As a result, diffraction signals at larger scattering angles could be detected, revealing additional information on the three-dimensional shapes of the droplets. These latest experiments utilized the new "LAMP" soft x-ray end station [22][23]. Experiments with beams of helium nanodroplets have been extensively documented elsewhere [24][25][26][27].…”

Section: Methodsmentioning

confidence: 99%

Shapes of rotating superfluid helium nanodroplets

et al. 2017

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Rotating superfluid He droplets of approximately 1 μm in diameter were obtained in a free nozzle beam expansion of liquid He in vacuum and were studied by single-shot coherent diffractive imaging using an x-ray free electron laser. The formation of strongly deformed droplets is evidenced by large anisotropies and intensity anomalies (streaks) in the obtained diffraction images. The analysis of the images shows that, in addition to previously described axially symmetric oblate shapes, some droplets exhibit prolate shapes. Forward modeling of the diffraction images indicates that the shapes of rotating superfluid droplets are very similar to their classical counterparts, giving direct access to the droplet angular momenta and angular velocities. The analyses of the radial intensity distribution and appearance statistics of the anisotropic images confirm the existence of oblate metastable superfluid droplets with large angular momenta beyond the classical bifurcation threshold.3

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Section: Methodsmentioning

confidence: 99%

Shapes of rotating superfluid helium nanodroplets

et al. 2017

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“…1. The experiment was performed at the Linac Coherent Light Source (LCLS) using the Atomic, Molecular, and Optical (AMO) physics end station [43]. The pump and probe x-ray pulses with a controlled time delay were generated at 120 Hz using single electron bunches and split undulator sections as described in Ref.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

et al. 2016

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The capability of generating two intense, femtosecond x-ray pulses with a controlled time delay opens the possibility of performing time-resolved experiments for x-ray-induced phenomena. We have applied this capability to study the photoinduced dynamics in diatomic molecules. In molecules composed of low-Z elements, K-shell ionization creates a core-hole state in which the main decay mode is an Auger process involving two electrons in the valence shell. After Auger decay, the nuclear wave packets of the transient two-valence-hole states continue evolving on the femtosecond time scale, leading either to separated atomic ions or long-lived quasibound states. By using an x-ray pump and an x-ray probe pulse tuned above the K-shell ionization threshold of the nitrogen molecule, we are able to observe ion dissociation in progress by measuring the time-dependent kinetic energy releases of different breakup channels. We simulated the measurements on N 2 with a molecular dynamics model that accounts for K-shell ionization, Auger decay, and the time evolution of the nuclear wave packets. In addition to explaining the time-dependent feature in the measured kinetic energy release distributions from the dissociative states, the simulation also reveals the contributions of quasibound states.

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“…The fluence is varied between 10 10 photons /μm 2 and 10 13 photons /μm 2 . The number of soft-x-ray photons per pulse generated by currently operating XFELs is up to 10 13 photons at LCLS AMO [44] and is expected to be up to 2 × 10 14 photons at European XFEL SQS [45], and a typical focal area is few μm 2 for soft x-rays [2]. Thus, a peak fluence approaching 10 13 photons /μm 2 is realistic.…”

Section: Introductionmentioning

confidence: 99%

Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse

et al. 2018

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With the highly intense x-ray light generated by x-ray free-electron lasers (XFELs), molecular samples can be ionized many times in a single pulse. Here we report on a computational study of molecular spectroscopy at the high x-ray intensity provided by XFELs. Calculated photoelectron, Auger electron, and x-ray fluorescence spectra are presented for a single water molecule that reaches many electronic hole configurations through repeated ionization steps. The rich details shown in the spectra depend on the x-ray pulse parameters in a nonintuitive way. We discuss how the observed trends can be explained by the competition of microscopic electronic transition processes. A detailed comparison between spectra calculated within the independent-atom model and within the molecular-orbital framework highlights the chemical sensitivity of the spectral lines of multiple-hole configurations. Our results demonstrate how x-ray multiphoton ionization-related effects such as charge-rearrangement-enhanced x-ray ionization of molecules and frustrated absorption manifest themselves in the electron and fluorescence spectra.

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The Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source

Cited by 68 publications

References 26 publications

Shapes of rotating superfluid helium nanodroplets

Shapes of rotating superfluid helium nanodroplets

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse

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