4D multiple-cathode ultrafast electron microscopy
Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging.
Additional Information© 2014 National Academy of Sciences. Freely available online through the PNAS open access option. Contributed by Ahmed H. Zewail, June 20, 2014 (sent for review June 6, 2014). Published ahead of print July 8, 2014. We thank Erik Kieft and Robert Murphy of FEI for their assistance in the modification of microscope control electronics. This work was supported by the National Science Foundation (DMR-0964886) and the Air Force Office of Scientific Research (FA9550-11-1-0055) in the Gordon and Betty Moore Center for Physical Biology at the California Institute of Technology. Author contributions: J.S.B., H.L., and A.H.Z. designed research, performed research, and wrote the paper. The authors declare no conflict of interest.
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