Direct Imaging of Transient Molecular Structures with Ultrafast Diffraction

Ihee, Hyotcherl; Lobastov, Vladimir A.; Gómez, U.; Goodson, Boyd M.; Srinivasan, Ramesh; Ruan, Chong‐Yu; Zewail, Ahmed H.

doi:10.1126/science.291.5503.458

Cited by 497 publications

(377 citation statements)

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“…The combination with simulations allowed for the deduction of further values, such as the coherence length and pulse duration of the propagated electron pulses. Compared to other sources with time resolutions on the order of 1 ps or below [7,8], our setup did produce electron pulses with 1.5 ps duration for few electrons/pulse. More importantly, our table-top setup allows for a stable production of > 10 6 electrons/pulse at a repetition rate of 1 kHz with an estimated pulse durations of 60 ps.…”

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confidence: 99%

“…Here, electrons were created from metallic surfaces by short laser pulses and accelerated in dc electric fields [7,8], yielding sub-picosecond electron pulses of moderate coherence and brilliance. Radio-frequency cavities allow for temporal compression of electron pulses through phase-space rotation, shortening the pulse duration to below 100 fs with electron numbers of 10 6 per pulse and electron spot sizes below 100 µm [30].…”

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confidence: 99%

“…Furthermore, electron diffraction has found broad application for gas-phase structuredetermination in chemistry [5]. Recent developments have mainly focused on realizing time-resolved experiments in order to study structural dynamics, where xray and electron diffraction served as complementary approaches [6][7][8][9][10][11].To be able to record structural changes during ultrafast molecular processes of small complex molecules in the gas phase, signals from many identical molecules have to be averaged. Gas-phase investigations pose the challenge that the sample might comprise different isomers and sizes [12].…”

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Electron gun for diffraction experiments off controlled molecules

Müller¹,

Trippel²,

Długołȩcki³

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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A dc electron gun, generating picosecond pulses with up to 8 × 10 6 electrons per pulse, was developed. Its applicability for future time-resolved-diffraction experiments on state-and conformer-selected laser-aligned or oriented gaseous samples was characterized. The focusing electrodes were arranged in a velocity-map imaging spectrometer configuration. This allowed to directly measure the spatial and velocity distributions of the electron pulses emitted from the cathode. The coherence length and pulse duration of the electron beam were characterized by these measurements combined with electron trajectory simulations. Electron diffraction data off a thin aluminum foil illustrated the coherence and resolution of the electron-gun setup.Diffractive imaging is a promising approach to unravel the microscopic details of chemical processes through the recording of so-called molecular movies in the gasphase, which trace the structural dynamics of individual molecules and nano-particles at the atomic level. Electron and x-ray diffraction are well established tools to investigate the structures of solid state samples [1], for example in transmission electron microscopy [2] or xray crystallography [3,4]. Furthermore, electron diffraction has found broad application for gas-phase structuredetermination in chemistry [5]. Recent developments have mainly focused on realizing time-resolved experiments in order to study structural dynamics, where xray and electron diffraction served as complementary approaches [6][7][8][9][10][11].To be able to record structural changes during ultrafast molecular processes of small complex molecules in the gas phase, signals from many identical molecules have to be averaged. Gas-phase investigations pose the challenge that the sample might comprise different isomers and sizes [12]. In addition, the molecules in the gas phase are typically randomly oriented. It is therefore important to provide samples, which are as clean and defined as possible, to allow for experimental averaging over multiple electron pulses. Clean molecular samples can be generated by their spatial separation according to shape [13][14][15] and size [16]. Controlling the spatial orientation of the molecules leads to an enhancement of the information that can be retrieved from a diffraction pattern, as proposed theoretically [17][18][19][20] and demonstrated experimentally for x-ray [21,22] as well as for electron diffraction [23,24]. Strong alignment or orientation is generally necessary [11,20] for three-dimensional structure reconstruction [24] and can be provided in cold supersonic molecular beams by strong-field laser alignment and mixed-field orientation [25][26][27][28][29]. The low density of these controlled gas-phase samples requires sources of large-cross-section particles or photons with large brightness, while still ensuring atomic resolution. Electron sources can meet these requirements even in table-top setups.The first sources for creating electron pulses short enough to study ultrafast processes in molecules o...

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confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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Electron gun for diffraction experiments off controlled molecules

Müller¹,

Trippel²,

Długołȩcki³

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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“…Femtosecond electron bunches generated from SURIYA set-up can be used for direct applications such as electron diffraction [2], or to produce either farinfrared (FIR) radiation or femtosecond X-ray pulses [3,4]. The SURIYA project set-up is located at the basement of the FNRF building for radiation shielding reason.…”

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Beam Characterizations at Femtosecond Electron Beam Facility

Rimjaem

Jinamoon²,

Kangrang³

et al.

Proceedings of the 2005 Particle Accelerator Conference

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The SURIYA project at the Fast Neutron Research Facility (FNRF) has been established and is being commissioning to generate femtosecond (fs) electron bunches. Theses short bunches are produced by a system consisting of an S-band thermionic cathode RF-gun, an alpha magnet (α-magnet) serving as a magnetic bunch compressor, and a SLAC-type linear accelerator (linac). The characteristics of its major components and the beam characterizations as well as the preliminary experimental results will be presented and discussed in this paper.

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Ultrafast Electron Diffraction of Transient [Fe(CO)4]: Determination of Molecular Structure and Reaction Pathway

2001

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Transition metal carbonyl complexes [1,2] respond to ultraviolet light by the loss of one or more CO ligands and subsequent formation of coordinatively unsaturated carbonyl complexes, which are known to catalyze a variety of reactions. [3±5] The photochemistry governing the formation of these coordinatively unsaturated species has been an active area of research both experimentally [6±13] and theoretically, [14±19] often focusing on the reaction pathways and molecular structures of these transient species. Among transition metal carbonyl complexes, [Fe(CO) 5 ] is one of the most extensively studied molecular systems. [Fe(CO) 5 ] absorbs strongly in the ultraviolet starting at about 350 nm (3.5 eV). [18, 20±22] The spectrum is rather featureless, and is dominated by metal-toligand charge transfer transitions [18] at high energies. Having five carbonyl ligands, an [Fe(CO) 5 ] molecule can dissociate into five different products ([Fe(CO) x ], x 4, 3, 2, 1, 0) depending on the excitation wavelength.In these reactions, [Fe(CO) 4 ] is the primary intermediate and serves as a ªdoorwayº molecule for various subsequent reactions, [23,24] such as decomposition, recombination with the carbonyl ligand, and coordination with solvent molecules. Elucidating the nature of [Fe(CO) 4 ], including its electronic states and the corresponding molecular geometry, is important for understanding the role of intermediates in the photolysis of transition metal carbonyl complexes.Herein we report the direct determination of the molecular structure ( Figure 1) of transient [Fe(CO) 4 ] using diffraction with ultrashort pulses of electrons. In this way, we are able to identify the primary reaction pathway and provide details of

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Direct Imaging of Transient Molecular Structures with Ultrafast Diffraction

Cited by 497 publications

References 23 publications

Electron gun for diffraction experiments off controlled molecules

Electron gun for diffraction experiments off controlled molecules

Beam Characterizations at Femtosecond Electron Beam Facility

Ultrafast Electron Diffraction of Transient [Fe(CO)4]: Determination of Molecular Structure and Reaction Pathway

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