Imaging of Isolated Molecules with Ultrafast Electron Pulses

Hensley, Christopher J.; Yang, Jie; Centurion, Martin

doi:10.1103/physrevlett.109.133202

Cited by 169 publications

(186 citation statements)

References 24 publications

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“…From these results we have approximately determined the bond distances for the three molecules and their corresponding molecular cations. Thus, the present work provides an alternative and a complement to gas-phase electron diffraction (GED) techniques, [27][28][29][30] which have been successfully used to retrieve three-dimensional structural information from molecules in the gas phase but would be difficult to apply to molecular cations.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular photoelectron diffraction in the gas phase

Ueda

Miron

Plésiat

et al. 2013

The Journal of Chemical Physics

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We report unambiguous experimental and theoretical evidence of intramolecular photoelectron diffraction in the collective vibrational excitation that accompanies high-energy photoionization of gas-phase CF 4 , BF 3 , and CH 4 from the 1s orbital of the central atom. We show that the ratios between vibrationally resolved photoionization cross sections (v-ratios) exhibit pronounced oscillations as a function of photon energy, which is the fingerprint of electron diffraction by the surrounding atomic centers. This interpretation is supported by the excellent agreement between first-principles static-exchange and time-dependent density functional theory calculations and high resolution measurements, as well as by qualitative agreement at high energies with a model in which atomic displacements are treated to first order of perturbation theory. The latter model allows us to rationalize the results for all the v-ratios in terms of a generalized v-ratio, which contains information on the structure of the above three molecules and the corresponding molecular cations. A fit of the measured v-ratios to a simple formula based on this model suggests that the method could be used to obtain structural information of both neutral and ionic molecular species.

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Section: Introductionmentioning

confidence: 99%

Intramolecular photoelectron diffraction in the gas phase

Ueda

Miron

Plésiat

et al. 2013

The Journal of Chemical Physics

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“…It is, however, so far not possible to experimentally produce perfectly aligned molecules in the gas phase for diffraction experiments. We have recently shown that partial alignment, achieved with a femtosecond laser pulse, is sufficient to retrieve the structure of small molecules in a field-free environment [15,16]. While it has not yet been shown that this method can be applied to large molecules, it is clear that diffraction patterns even with partial alignment provide more structural information than diffraction patterns from randomly oriented molecules.…”

Section: Introductionmentioning

confidence: 99%

“…The first experiments showed anisotropy in the diffraction patterns when the molecules are aligned with nanosecond laser pulses [18] and when a dissociation reaction is triggered with a femtosecond UV laser pulse [19,20]. More recently, diffraction from impulsively aligned molecules has been demonstrated both with electrons [15] and with X-rays [21].…”

Section: Introductionmentioning

confidence: 99%

Gas-phase electron diffraction from laser-aligned molecules

Yang

Centurion

2015

Struct Chem

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Electron diffraction is a valuable tool to capture structural information from molecules in the gas phase. However, the information contained in the diffraction patterns is limited due to the random orientation of the molecules. Additional structural information can be retrieved if the molecules are aligned. Molecules can be impulsively aligned with femtosecond laser pulses, producing a transient alignment. The alignment persists only for a time on the order of a picosecond, so a pulsed electron gun is needed to record the diffraction patterns. In this manuscript, we describe the alignment process and show the changes in the diffraction pattern as a result of alignment. Carbon disulfide, a linear molecule, was chosen as a model molecule for these experiments. We have also experimentally investigated the temporal evolution of the alignment and the dependence on the laser pulse intensity.

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“…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].…”

mentioning

confidence: 99%

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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Imaging of Isolated Molecules with Ultrafast Electron Pulses

Cited by 169 publications

References 24 publications

Intramolecular photoelectron diffraction in the gas phase

Intramolecular photoelectron diffraction in the gas phase

Gas-phase electron diffraction from laser-aligned molecules

Electron gun for diffraction experiments off controlled molecules

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