Ultrafast electron diffraction

<h2 id="history">History</h2>
<p>The design of early ultrafast electron diffraction instruments was based on X-ray streak cameras, the first reported ultrafast electron diffraction experiment demonstrating an electron pulse length of 100 picoseconds (10–10 seconds).<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> The temporal resolution of ultrafast electron diffraction has been reduced to the attosecond (10–18 second) time scale to perform attosecond electron diffraction measurements which reveal electron motion dynamics.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p>
<h2 id="electron-pulse-production">Electron Pulse Production</h2>
<p>The electron pulses are typically produced by the process of photoemission in which a femtosecond optical pulse is directed toward a <a href="/facts/Photocathode/XPcNlAjs">photocathode</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>  If the incident laser pulse has an appropriate energy, electrons will be ejected from the photocathode through a process known as photoemission. The electrons are subsequently accelerated to high energies, ranging from tens of kiloelectron-volts<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> to several megaelectron-volts,<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> using an <a href="/facts/Electron_gun/l6nahAeW">electron gun</a>.
</p>
<h2 id="electron-pulse-compression">Electron Pulse Compression</h2>
<p>Generally, two methods are used in order to compress electron pulses in order to overcome pulsewidth expansion due to Coulomb repulsion.  Generating high-flux ultrashort electron beams has been relatively straightforward, but pulse duration below a picosecond proved extremely difficult due to space-charge effects. Space-charge interactions increase in severity with bunch charge and rapidly act to broaden the pulse duration, which has resulted in an apparently unavoidable trade-off between signal (bunch charge) and time-resolution in ultrafast electron diffraction experiments.  Radio-frequency (RF) compression has emerged has an leading method of reducing the pulse expansion in ultrafast electron diffraction experiments, achieving temporal resolution well below 50 femtoseconds.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
Shorter electron beams below 10 femtoseconds are ultimately required to probe the fastest dynamics
in solid state materials and observe gas phase molecular reactions.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p>
<h2 id="single-shot">Single shot</h2>

<p>For studying irreversible process, a diffraction signal is obtained from a single electron bunch containing 
  
    
      
        
          10
          
            5
          
        
      
    
    {\displaystyle 10^{5}}
  
 or more particles.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
<h2 id="stroboscopic">Stroboscopic</h2>
<p>When studying reversible process, especially weak signals caused by, e.g., thermal diffuse scattering, a diffraction pattern is accumulated from many electron bunches, as many as 
  
    
      
        
          10
          
            8
          
        
      
    
    {\displaystyle 10^{8}}
  
.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>
</p>
<h2 id="resolution">Resolution</h2>
<p>The resolution of an ultrafast electron diffraction apparatus can be characterized both in space and in time. Spatial resolution comes in two distinct parts: real space and <a href="/facts/Reciprocal_space/jYCjcEpH">reciprocal space</a>. Real space resolution is determined by the physical size of the electron probe on the sample. A smaller physical probe size can allow experiments on crystals that cannot feasibly be grown in large sizes.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a>
</p><p>High reciprocal space resolution allows for the detection of <a href="/facts/Bragg_diffraction/qEYANzQg">Bragg diffraction</a> spots that correspond to long periodicity phenomena. It can be calculated with the following equation:<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a>
</p>

Δ
        s
        =
        
          
            
              2
              π
            
            
              λ
              
                e
              
            
          
        
        
          
            
              ε
              
                n
              
            
            
              σ
              
                x
              
            
          
        
      
    
    {\displaystyle \Delta s={\frac {2\pi }{\lambda _{e}}}{\frac {\varepsilon _{n}}{\sigma _{x}}}}
  
,
<p>where Δ<i>s</i> is the reciprocal space resolution, λ<i>e</i> is the <a href="/facts/Compton_wavelength/og2h1J2q">Compton wavelength</a> of the electrons, ϵ<i>n</i> is the normalized <a href="/facts/Beam_emittance/r2RFcRs4">emittance</a> of the electrons, and σ<i>x</i> is the size of the probe on the sample.
</p><p>Temporal resolution is primarily a function of the bunch length of the electrons and the relative timing jitters between the pump and probe.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Ahmed_Zewail/aKJuw0a7">Ahmed Zewail</a></li>
<li><a href="/facts/R._J._Dwayne_Miller/Q7g9ndDW">R. J. Dwayne Miller</a></li>
<li><a href="/facts/Time_resolved_crystallography/sSME5P0h">Time resolved crystallography</a></li></ul>

<h2 id="sources">Sources</h2>
<ul><li>Srinivasan, Ramesh; Lobastov, Vladimir A.; Ruan, Chong-Yu; Zewail, Ahmed H. (2003). "Ultrafast Electron Diffraction (UED): A New Development for the 4D Determination of Transient Molecular Structures". <i><a href="/facts/Helvetica_Chimica_Acta/ALgfCoxa">Helvetica Chimica Acta</a></i>. 86 (6): 1761. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1002%2Fhlca.200390147">10.1002/hlca.200390147</a>.</li></ul>
<ul><li>Sciani, Germain; Miller, R.J. Dwayne (2011). "Femtosecond electron diffraction: heralding the era of atomically resolved dynamics". <i><a href="/facts/Reports_on_Progress_in_Physics/dEpu5erp">Reports on Progress in Physics</a></i>. 74 (9): 096101. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/2011RPPh...74i6101S">2011RPPh...74i6101S</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1088%2F0034-4885%2F74%2F9%2F096101">10.1088/0034-4885/74/9/096101</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:121497071">121497071</a>.</li>
<li>Chatelain, Robert P.; Morrison, Vance R.; Godbout, Chris; Siwick, Bradley J. (2012). "Ultrafast electron diffraction with radio-frequency compressed electron pulses". <i><a href="/facts/Applied_Physics_Letters/oIQvp1Wg">Applied Physics Letters</a></i>. 101 (8): 081901. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/2012ApPhL.101h1901C">2012ApPhL.101h1901C</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1063%2F1.4747155">10.1063/1.4747155</a>.</li>
<li></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Mourou, Gerard; Williamson, Steve (1982). "Picosecond electron diffraction". Applied Physics Letters. 41 (1): 44. Bibcode:1982ApPhL..41...44M. doi:10.1063/1.93316. <a href="/wiki/Applied_Physics_Letters" target="_blank">/wiki/Applied_Physics_Letters</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Hui, Dandan; Alqattan, Husain; Sennary, Mohamed; Golubev, Nikolay V.; Hassan, Mohammed Th. (2024-08-23). "Attosecond electron microscopy and diffraction". Science Advances. 10 (34). doi:10.1126/sciadv.adp5805. ISSN 2375-2548. PMC 11338230. PMID 39167650. <a href="https://www.science.org/doi/10.1126/sciadv.adp5805" target="_blank">https://www.science.org/doi/10.1126/sciadv.adp5805</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Srinivasan, R.; Lobastov, V.; Ruan, C.-Y.; Zewail, A. (2003). "Ultrafast Electron Diffraction (UED)". Helvetica. 86 (6): 1761–1799. doi:10.1002/hlca.200390147. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Siwick, Bradley J.; Dwyer, Jason R.; Jordan, Robert E.; Miller, R. J. Dwayne (21 Nov 2003). "An Atomic-Level View of Melting Using Femtosecond Electron Diffraction". Science. 302 (5649): 1382–1385. Bibcode:2003Sci...302.1382S. doi:10.1126/science.1090052. PMID 14631036. S2CID 4593938. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Weathersby, S. P. (2015). "Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory". Review of Scientific Instruments. 86 (7): 073702. Bibcode:2015RScI...86g3702W. doi:10.1063/1.4926994. PMID 26233391. S2CID 17652180. <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion" target="_blank">https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Qi, F. (2020). "Breaking 50 Femtosecond Resolution Barrier in MeV Ultrafast Electron Diffraction with a Double Bend Achromat Compressor". Physical Review Letters. 124 (13): 134803. arXiv:2003.08046. Bibcode:2020PhRvL.124m4803Q. doi:10.1103/PhysRevLett.124.134803. PMID 32302182. S2CID 212747515. <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.134803" target="_blank">https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.134803</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Gliserin, A. (2015). "Sub-phonon-period compression of electron pulses for atomic diffraction". Nat Commun. 6 (8723): 4. Bibcode:2015NatCo...6.8723G. doi:10.1038/ncomms9723. PMC 4640064. PMID 26502750. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640064" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640064</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>Siwick, Bradley J; Dwyer, Jason R; Jordan, Robert E; Miller, RJ Dwayne (2003). "An atomic-level view of melting using femtosecond electron diffraction". Science. 302 (5649): 1382–1385. Bibcode:2003Sci...302.1382S. doi:10.1126/science.1090052. PMID 14631036. S2CID 4593938. <a href="/wiki/Science_(journal)" target="_blank">/wiki/Science_(journal)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>de Cotret, Laurent P Ren{\'e}; Otto, Martin R; P{\"o}hls, Jan-Hendrik; Luo, Zhongzhen; Kanatzidis, Mercouri G; Siwick, Bradley J (2022). "Direct visualization of polaron formation in the thermoelectric SnSe". Proceedings of the National Academy of Sciences. 119 (3). arXiv:2111.10012. Bibcode:2022PNAS..11913967R. doi:10.1073/pnas.2113967119. PMC 8784136. PMID 35012983. S2CID 244463218. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8784136" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8784136</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
<li id="fn:10"><p>Bie, Ya-Qing; Zong, Alfred; Wang, Xirui; Jarillo-Herrero, Pablo; Gedik, Nuh (2021). "A versatile sample fabrication method for ultrafast electron diffraction". Ultramicroscopy. 230: 113389. doi:10.1016/j.ultramic.2021.113389. PMID 34530284. S2CID 237546671. <a href="https://doi.org/10.1016%2Fj.ultramic.2021.113389" target="_blank">https://doi.org/10.1016%2Fj.ultramic.2021.113389</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li>
<li id="fn:11"><p>Weathersby, S. P. (2015). "Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory". Review of Scientific Instruments. 86 (7): 073702. Bibcode:2015RScI...86g3702W. doi:10.1063/1.4926994. PMID 26233391. S2CID 17652180. <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion" target="_blank">https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li>
<li id="fn:12"><p>Weathersby, S. P. (2015). "Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory". Review of Scientific Instruments. 86 (7): 073702. Bibcode:2015RScI...86g3702W. doi:10.1063/1.4926994. PMID 26233391. S2CID 17652180. <a href="https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion" target="_blank">https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1022&context=physicscenturion</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li>
</ol>

Ultrafast electron diffraction open-in-new

Ultrafast electron diffraction