Femtosecond electron diffraction: ‘making the molecular movie’

Dwyer, Jason R.; Hebeisen, Christoph T.; Ernstorfer, Ralph; Harb, Maher; Deyirmenjian, V. B.; Jordan, Robert E.; Miller, R. J. Dwayne

doi:10.1098/rsta.2005.1735

Cited by 192 publications

(165 citation statements)

References 73 publications

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“…Our experimental data show a decrease in the diffraction intensity of 6-8%. The rate of melting process was estimated from our data to be 3 × 10 11 s −1 , which is in agreement with the previously reported values for thermal melting (27). Based on phonon/phonon and phonon/lattice interaction rates, which are in the 10 11 s −1 rate, and our XRD data, we assign the observed processing to thermal melting, rather than electronic melting.…”

Section: Resultssupporting

confidence: 80%

“…At high excitation fluence, melting of the gold crystal may occur near or above its melting point of 1,337.33 K. Time-resolved electron diffraction, X-ray scattering, and optical spectroscopy techniques (7,(24)(25)(26)(27)(28)(29) have been applied by previous investigators to study the melting process of gold nanocrystals. In this study, we report the observation of melting, annealing, and recrystallization of gold single crystal under femtosecond irradiation.…”

Section: Resultsmentioning

confidence: 99%

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Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

Chen

Tang

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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We utilize 100 fs optical pulses to induce ultrafast disorder of 35-to 150-nm thick single Au(111) crystals and observe the subsequent structural evolution using 0.6-ps, 8.04-keV X-ray pulses. Monitoring the picosecond time-dependent modulation of the X-ray diffraction intensity, width, and shift, we have measured directly electron/phonon coupling, phonon/lattice interaction, and a histogram of the lattice disorder evolution, such as lattice breath due to a pressure wave propagating at sonic velocity, lattice melting, and recrystallization, including mosaic formation. Results of theoretical simulations agree and support the experimental data of the lattice/liquid phase transition process. These time-resolved X-ray diffraction data provide a detailed description of all the significant processes induced by ultrafast laser pulses impinging on thin metallic single crystals.ultrafast X-ray diffraction | laser-induced phase transition | coherent phonon | annealing | grain growth L attice disorder and phase transition in metal, semiconductor, and alloy are of vital importance in both fundamental science and technology. Irradiation with femtosecond laser pulses induces lattice disorder (1), which could be (i) a purely electronic nonthermal order-disorder process by injecting carriers into bulk semiconductor crystals, such as Si (2, 3) and GaAs (4, 5) within 1 ps; (ii) a purely thermal-disorder thermal process that depends on electron/phonon, phonon/phonon, and phonon/lattice interaction time in metal films, especially in noble metals, such as Au (6, 7); (iii) a combination of thermal-and nonthermal-disorder with the ratio depending on the laser fluence (8). When the laser fluence is sufficient, the phase transition from solid to liquid will occur and the melting process is considered to involve both thermal and nonthermal processes, whereas in gold (9-11) and aluminum films, which is the dominant process is still under debate (12-14). The laser heating and melting of the gold film studies presented in this paper were induced by low excitation levels, therefore the electronic effects on the stability of the lattice are not expected to occur (15), which is in contrast to the high excitation levels used for electronic hardening in gold (10).In this paper, we describe experiments that utilize subpicosecond time-resolved X-ray diffraction (XRD) to measure directly the transient changes in the crystal structure induced by 400-nm, 100-fs laser pulses impinging upon the surface of 35-, 70-, and 150-nm-thick Au(111) single-crystal films. The experiments presented here may be assigned to a weak excitation region, at fluence lower than 15 mJ∕cm 2 , where the blast wave and coherent phonons were observed, and a strong excitation region, at fluencies of 37 mJ∕cm 2 and above, where melting occurs. In addition, a pressure blast wave, formed immediately upon excitation, induced lattice contraction (16) that propagated through the bulk of the crystal at sonic velocity, generating stress and the wellknown sonic wave. We will show that, i...

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

Chen

Tang

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…U ltrafast electron diffraction (UED) enables the study of molecular structural dynamics with atomic spatial resolution at picosecond timescales [1][2][3] . Determination of the structure and function of molecules is critical to understand all but the most simple chemical reaction pathways, to understand biochemical dynamics such as protein folding and regulation or to understand the formation of cracks in novel materials 4,5 .…”

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confidence: 99%

High-coherence picosecond electron bunches from cold atoms

et al. 2013

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Ultrafast electron diffraction enables the study of molecular structural dynamics with atomic resolution at subpicosecond timescales, with applications in solid-state physics and rational drug design. Progress with ultrafast electron diffraction has been constrained by the limited transverse coherence of high-current electron sources. Photoionization of laser-cooled atoms can produce electrons of intrinsically high coherence, but has been too slow for ultrafast electron diffraction. Ionization with femtosecond lasers should in principle reduce the electron pulse duration, but the high bandwidth inherent to short laser pulses is expected to destroy the transverse coherence. Here we demonstrate that a two-colour process with femtosecond excitation followed by nanosecond photoionization can produce picosecond electron bunches with high transverse coherence. Ultimately, the unique combination of ultrafast ionization, high coherence and three-dimensional bunch shaping capabilities of cold atom electron sources have the potential for realising the brightness and coherence requirements for single-shot electron diffraction from crystalline biological samples.

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“…The rate of the melting process was estimated, from the experimental data, to be 3 Â 10 11 s À1 , which is in agreement with the previously reported values for thermal melting. 63 Based on phonon/phonon and phonon/ lattice interaction rates, which are in the 10 11 s À1 rate, and the time-resolved XRD data, the observed process was assigned to thermal melting, rather than electronic melting. The increase in the XRD intensity from 92%-94%, starting at approximately 7 ps to $116% after 40 ps was attributed to recrystallization, mosaic crystal formation, and softening of the inner part of the crystal.…”

Section: Time Resolved X-ray Diffractionmentioning

confidence: 99%

Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine structure and x-ray absorption near edge structure

Chen

Rentzepis

2012

Journal of Applied Physics

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Ultrafast time resolved x-ray absorption and x-ray diffraction have made it possible to measure, in real time, transient phenomena structures and processes induced by optical femtosecond pulses. To illustrate the power of these experimental methods, we present several representative examples from the literature. (I) Time resolved measurements of photon/electron coupling, electron/phonon interaction, pressure wave formation, melting and recrystallization by means of time resolved x-ray diffraction. (II) Ultrafast x-ray absorption, EXAFS, for the direct measurement of the structures and their kinetics, evolved during electron transfer within molecules in liquid phase. (III) XANES experiments that measure directly pathway for the population of high spin states and the study of the operating mechanism of dye activated TiO2 solar cell devices. The construction and use of novel polycapillary x-ray lenses that focus and collimate hard x-rays efficiently are described.

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Femtosecond electron diffraction: ‘making the molecular movie’

Cited by 192 publications

References 73 publications

Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

High-coherence picosecond electron bunches from cold atoms

Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine structure and x-ray absorption near edge structure

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