P. Hommelhoff, C. Kealhofer, M. A. Kasevich,\u00a0Phys. Rev. Lett. 97<\/strong> 247402 (2006)<\/a><\/p><\/blockquote>\n Electron microscopy is a powerful tool for studying matter, with an enormous variety of imaging modalities and contrast mechanisms. \u00a0High resolution transmission electron microscopy can provide sufficient spatial resolution to directly observe the positions of atoms in a material, and simpler techniques such as electron diffraction also provide information about how the atoms are arranged.<\/p>\n When the electrons in a solid are excited with a short laser pulse, this can launch a change in the position of the atoms.\u00a0 Does the motion of the atoms lead or follow changes in the other physical properties (such as electrical and magnetic properties)?\u00a0 Observing what happens can provide insight into the interactions between electrons, nuclei, and spins in a material.\u00a0 This interplay is at the core of many difficult problems in condensed matter physics, including the quest to understand exotic materials like high-temperature superconductors.<\/p>\n Studying ultrafast processes is technologically challenging, in part because detectors respond orders of magnitude too slowly. \u00a0This is like to trying to photograph a moving object with a shutter speed that is too slow, as illustrated in the first picture of Emily and Iona juggling. \u00a0[Thank you to Ellery Galvin for taking the pictures!].<\/p>\n Pump-probe techniques can get around the slow-detector problem by using an ultrafast probe pulse, which only illuminates sample for a short time.\u00a0 An ultrafast pump pulse initiates dynamics in the system and is followed by an ultrafast probe pulse which interacts with the system and is then detected.\u00a0 Even though the detector measures for a long time, the probe only interacts for a short time so that the measured data reflects the state of the sample at the time it was probed.<\/p>\n","protected":false},"excerpt":{"rendered":" Low-emittance ultrafast electron sources An important figure of merit for an electron source is its emittance, which determines how well the electron beam can be collimated and focused. \u00a0Emittance is also related to the degree of coherence of the electron beam, which quantifies fringe contrast in an interference experiment.\u00a0\u00a0The highest resolution electron microscopes use low-emittance … Continue reading Research<\/span><\/a><\/p>\n","protected":false},"author":1623,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-50","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/pages\/50","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/users\/1623"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/comments?post=50"}],"version-history":[{"count":22,"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/pages\/50\/revisions"}],"predecessor-version":[{"id":241,"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/pages\/50\/revisions\/241"}],"wp:attachment":[{"href":"https:\/\/sites.williams.edu\/electron\/wp-json\/wp\/v2\/media?parent=50"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Background<\/h4>\n
Pump-Probe techniques<\/h3>\n
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