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Abstract
A review that summarizes the most recent technological developments in the field of ultrafast structural dynamics with focus on the use of ultrashort X-ray and electron pulses follows. Atomistic views of chemical processes and phase transformations have long been the exclusive domain of computer simulators. The advent of femtosecond (fs) hard X-ray and fs-electron diffraction techniques made it possible to bring such a level of scrutiny to the experimental area. The following review article provides a summary of the main ultrafast techniques that enabled the generation of atomically resolved movies utilizing ultrashort X-ray and electron pulses. Recent advances are discussed with emphasis on synchrotron-based methods, tabletop fs-X-ray plasma sources, ultrabright fs-electron diffractometers, and timing techniques developed to further improve the temporal resolution and fully exploit the use of intense and ultrashort X-ray free electron laser (XFEL) pulses.
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Miller RJD. Ultrafast imaging of photochemical dynamics: roadmap to a new conceptual basis for chemistry. Faraday Discuss 2018; 194:777-828. [PMID: 27991637 DOI: 10.1039/c6fd00241b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- R J Dwayne Miller
- The Max Planck Institute for the Structure and Dynamics of Matter, The Hamburg Centre for Ultrafast Imaging, Luruper Chausse 149, Hamburg 22607, Germany. and Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, Ontario L5G 3J6, Canada
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3
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Ischenko AA, Weber PM, Miller RJD. Capturing Chemistry in Action with Electrons: Realization of Atomically Resolved Reaction Dynamics. Chem Rev 2017; 117:11066-11124. [DOI: 10.1021/acs.chemrev.6b00770] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Anatoly A. Ischenko
- Institute
of Fine Chemical Technologies, Moscow Technological University, Vernadskogo
86, 119571 Moscow, Russia
| | - Peter M. Weber
- Department
of Chemistry, Brown University, 324 Brook Street, 02912 Providence, Rhode Island, United States
| | - R. J. Dwayne Miller
- The Max Planck Institute for the Structure and Dynamics of Matter, Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
- Departments
of Chemistry and Physics, University of Toronto, 80 St. George, M5S 3H6 Toronto, Canada
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Meng X. Estimation of visibility of phase contrast with extraction voltages for field emission gun electron microscopes. Ultramicroscopy 2016; 173:14-15. [PMID: 27898298 DOI: 10.1016/j.ultramic.2016.11.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 10/19/2016] [Accepted: 11/17/2016] [Indexed: 10/20/2022]
Abstract
Estimation was made for visibility of phase contrast with varying extraction voltages. The resulting decay rates of visibility show that images with low image contrast from cryo EM will be seriously impacted with high extraction voltages.
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Affiliation(s)
- Xing Meng
- WsystemSolution, P.O.Box 3300 Latham, 12110-9998 NY, United States.
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Sparkes BM, Thompson DJ, McCulloch AJ, Murphy D, Speirs RW, Torrance JSJ, Scholten RE. High-coherence electron and ion bunches from laser-cooled atoms. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:1008-1014. [PMID: 24758916 DOI: 10.1017/s1431927614000774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Cold atom electron and ion sources produce electron bunches and ion beams by photoionization of laser-cooled atoms. They offer high coherence and the potential for high brightness, with applications including ultra-fast electron-diffractive imaging of dynamic processes at the nanoscale. The effective brightness of electron sources has been limited by nonlinear divergence caused by repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that electron bunches with ellipsoidal shape and uniform density distribution have linear internal Coulomb fields, such that the Coulomb explosion can be reversed using conventional optics. Our source can create bunches shaped in three dimensions and hence in principle achieve the transverse spatial coherence and brightness needed for picosecond-diffractive imaging with nanometer resolution. Here we present results showing how the shaping capability can be used to measure the spatial coherence properties of the cold electron source. We also investigate space-charge effects with ions and generate electron bunches with durations of a few hundred picoseconds. Future development of the cold atom electron and ion source will increase the bunch charge and charge density, demonstrate reversal of Coulomb explosion, and ultimately, ultra-fast coherent electron-diffractive imaging.
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Affiliation(s)
- Ben M Sparkes
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Daniel J Thompson
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Andrew J McCulloch
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Dene Murphy
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Rory W Speirs
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Joshua S J Torrance
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
| | - Robert E Scholten
- School of Physics,ARC Centre of Excellence for Coherent X-Ray Science,The University of Melbourne,Parkville,VIC 3010,Australia
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Analytical model of an isolated single-atom electron source. Ultramicroscopy 2014; 147:61-9. [PMID: 25062039 DOI: 10.1016/j.ultramic.2014.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 06/26/2014] [Accepted: 07/06/2014] [Indexed: 11/20/2022]
Abstract
An analytical model of a single-atom electron source is presented, where electrons are created by near-threshold photoionization of an isolated atom. The model considers the classical dynamics of the electron just after the photon absorption, i.e. its motion in the potential of a singly charged ion and a uniform electric field used for acceleration. From closed expressions for the asymptotic transverse electron velocities and trajectories, the effective source temperature and the virtual source size can be calculated. The influence of the acceleration field strength and the ionization laser energy on these properties has been studied. With this model, a single-atom electron source with the optimum electron beam properties can be designed. Furthermore, we show that the model is also applicable to ionization of rubidium atoms, and thus also describes the ultracold electron source, which is based on photoionization of laser-cooled alkali atoms.
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Miller RJD. Mapping atomic motions with ultrabright electrons: the chemists' gedanken experiment enters the lab frame. Annu Rev Phys Chem 2014; 65:583-604. [PMID: 24423377 DOI: 10.1146/annurev-physchem-040412-110117] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review documents the development of high-bunch charge electron pulses with sufficient combined spatiotemporal resolution and intensity to literally light up atomic motions. This development holds promise in coming to a first-principles understanding of diverse problems, ranging from molecular reaction dynamics and structure-function correlations in biology to cooperativity in strongly correlated electron-lattice systems. It is now possible to directly observe the key modes involved in propagating structural changes and the enormous reduction in dimensionality that occurs in barrier crossing regions, which is central to chemistry and makes reaction mechanisms transferrable concepts. This information will help direct theoretical advances that will undoubtedly lead to generalized principles with respect to scaling relations in structural dynamics that will bridge chemistry to biology. In this quest, the limitations and future directions for further development are discussed to give an overview of the present status of the field.
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Affiliation(s)
- R J Dwayne Miller
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany, and Departments of Chemistry and Physics, University of Toronto, Toronto, Ontario M5S 3H6, Canada;
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Engelen WJ, Smakman EP, Bakker DJ, Luiten OJ, Vredenbregt EJD. Effective temperature of an ultracold electron source based on near-threshold photoionization. Ultramicroscopy 2014; 136:73-80. [PMID: 24012938 DOI: 10.1016/j.ultramic.2013.07.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/11/2013] [Accepted: 07/19/2013] [Indexed: 11/28/2022]
Affiliation(s)
- W J Engelen
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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McCulloch AJ, Sheludko DV, Junker M, Scholten RE. High-coherence picosecond electron bunches from cold atoms. Nat Commun 2013; 4:1692. [PMID: 23591859 DOI: 10.1038/ncomms2699] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 03/05/2013] [Indexed: 11/09/2022] Open
Abstract
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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Affiliation(s)
- A J McCulloch
- Centre of Excellence for Coherent X-ray Science, School of Physics, University of Melbourne, Melbourne, Victoria 3010, Australia
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High-coherence electron bunches produced by femtosecond photoionization. Nat Commun 2013; 4:1693. [PMID: 23591860 DOI: 10.1038/ncomms2700] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 03/05/2013] [Indexed: 11/08/2022] Open
Abstract
With the development of ultrafast electron and X-ray sources it is becoming possible to study structural dynamics with atomic-level spatial and temporal resolution. Because of their short mean free path, electrons are particularly well suited for investigating surfaces and thin films, such as the challenging and important class of membrane proteins. To perform single-shot diffraction experiments on protein crystals, an ultracold electron source was proposed, based on near-threshold photoionization of laser-cooled atoms, which is capable of producing electron pulses of both high intensity and high coherence. Here we show that high coherence electron pulses can be produced by femtosecond photoionization, opening up a new regime of ultrafast structural dynamics experiments. The transverse coherence turns out to be much better than expected on the basis of the large bandwidth of the femtosecond ionization laser pulses. This surprising result can be explained by analysis of classical electron trajectories.
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