Short X-ray pulses from third-generation light sources

Степанов, А. Л.; Hauri, Christoph P.

doi:10.1107/s1600577515019281

Cited by 7 publications

(5 citation statements)

References 69 publications

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“…Some examples of XAS facilities are synchrotrons, − X-ray free electron lasers (XFELS), − and various tabletop sources. − A number of these sources are compatible with time-resolved measurements for studies of electron and nuclear dynamics. For example, third generation synchrotrons offer time resolutions on the order of 50–100 ps. , Slicing schemes can enable time resolution down to femtoseconds, although with a significant loss of flux. − XFELS provide extremely high flux and pulse durations of tens of femtoseconds, with the recent possibility for subfemtosecond pulses. , All of these methods contribute significantly to understanding photoinduced dynamics in molecules and materials. An exciting area of recent activity is centered on performing ultrafast, element-specific measurements using XUV light.…”

Section: Xuv Reflection–absorption Spectroscopymentioning

confidence: 99%

“…For example, third generation synchrotrons offer time resolutions on the order of 50−100 ps. 113,117 Slicing schemes can enable time resolution down to femtoseconds, although with a significant loss of flux. 117−119 XFELS provide extremely high flux and pulse durations of tens of femtoseconds, with the recent possibility for subfemtosecond pulses.…”

Section: Xuv Reflection−absorption Spectroscopymentioning

confidence: 99%

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Small Polarons and Surface Defects in Metal Oxide Photocatalysts Studied Using XUV Reflection–Absorption Spectroscopy

et al. 2020

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In photocatalytic transition metal oxides, the surface electronic structure and carrier kinetics are complicated by both charge trapping at defects and self-trapping by small polaron formation. These effects are specific to both the material and the type of defect or surface states involved. Here we review recent studies on ultrafast photoexcited charge carrier dynamics at the surfaces of α-Fe 2 O 3 (hematite) and NiO and at the interface of a α-Fe 2 O 3 /NiO heterojunction using extreme ultraviolet (XUV) reflection−absorption spectroscopy. We study the dynamics of small polaron formation at hematite surfaces showing that the rate of carrier self-trapping is slower than in the bulk due to a greater lattice reorganization energy required for surface polaron formation. We also show that surface dynamics of hematite can be systematically tuned to control carrier transport properties through surface functionalization. To better understand the impact of defects on carrier events, we study charge carrier recombination of NiO. It is shown that O vacancies have no detrimental effect on carrier lifetime while grain boundaries cause fast recombination. Finally, we study a model heterojunction consisting of α-Fe 2 O 3 and NiO and find that interfacial charge transfer across these two materials occurs by a two-step mechanism where the interfacial electric field drives fast exciton dissociation followed by hole injection from α-Fe 2 O 3 to NiO. These examples illustrate future opportunities to observe surface electron dynamics in photocatalytic materials with element and chemical state resolution using ultrafast XUV spectroscopy.

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Section: Xuv Reflection–absorption Spectroscopymentioning

confidence: 99%

Section: Xuv Reflection−absorption Spectroscopymentioning

confidence: 99%

Small Polarons and Surface Defects in Metal Oxide Photocatalysts Studied Using XUV Reflection–Absorption Spectroscopy

et al. 2020

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“…The development of ultrashort X-ray pulse sources (Stepanov & Hauri, 2016) stimulated development of the diffraction theory of such pulses. An interesting effect in this context is the slight stretching of pulses after diffraction.…”

Section: Introductionmentioning

confidence: 99%

X-ray pulse stretching after diffraction

Hrdý

2020

J Appl Cryst

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The development of ultrashort X-ray pulse sources requires optics that keep the pulse length as short as possible. One source of pulse stretching is the penetration of the pulse into a crystal during diffraction. Another source is the inclination of the intensity front when the diffraction is asymmetric. The theory of short X-ray pulse diffraction has been well developed by many authors. As it is rather complicated, it is sometimes difficult to foresee the pulse behavior (mainly stretching) during diffraction in various crystal arrangements. In this article, a simple model is suggested that gives a qualitatively similar shape to the diffracted pulse which follows from exact theory. It allows proposal of what experimental arrangement is optimal to minimize the pulse stretching during diffraction. First, the effect of pulse stretching due to penetration into a crystal surface is studied. On the basis of this, the pulse profile change during diffraction by two crystals, either symmetric or asymmetric, is predicted.

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“…Recent technological advances have enabled the generation of intense, short, coherent x-ray radiation using synchrotrons [1][2][3], laser-driven plasmas [4][5][6], and freeelectron lasers [7][8][9]. Consequently, various aspects of x-ray physics and chemistry have been explored with these new x-ray sources [10,11].…”

Section: Introductionmentioning

confidence: 99%

Violation of centrosymmetry in time-resolved coherent x-ray diffraction from rovibrational states of diatomic molecules

Shao

Starace

2019

Phys. Rev. A

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Owing to increasing applications of time-resolved coherent x-ray scattering for the investigation of molecular reaction dynamics, we develop a theoretical model for time-dependent x-ray diffraction from molecular and/or electronic motion in molecules. Our model shows that the violation of centrosymmetry (voc) is a general phenomenon in time-resolved diffraction patterns. We employ our theoretical model to illustrate the voc in time-resolved coherent x-ray diffraction from two oriented diatomic molecules undergoing ro-vibrational motion: lithium hydride (LiD) and hydrogen (HD). Our simulations show asymmetric x-ray diffraction images that reflect the directions of the molecular motions.

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Short X-ray pulses from third-generation light sources

Cited by 7 publications

References 69 publications

Small Polarons and Surface Defects in Metal Oxide Photocatalysts Studied Using XUV Reflection–Absorption Spectroscopy

Small Polarons and Surface Defects in Metal Oxide Photocatalysts Studied Using XUV Reflection–Absorption Spectroscopy

X-ray pulse stretching after diffraction

Violation of centrosymmetry in time-resolved coherent x-ray diffraction from rovibrational states of diatomic molecules

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