| TECHNOLOGY |
Ultrafast electron microscopy By integrating fast laser methods with transmission electron microscopy (TEM), researchers at Caltech have developed a microscopy technique that combines Angstrom spatial resolution with femtosecond time resolution (Proc. Natl. Acad. Sci. USA 2005, 102, 7069). The procedure, which was developed by Ahmed H. Zewail, Vladimir A. Lobastov, and Ramesh Srinivasan, has been used to image various types of samples including gold crystals, amorphous carbon, and cells from rat intestines. Unlike conventional TEM, in which a hot cathode supplies electrons continuously via thermionic emission, in the Caltech method, electron emission is caused by illuminating the cathode with weak femtosecond laser pulses. Because it liberates very few electrons per pulse, the procedure sidesteps some of the difficulties that tend to broaden the electron beam and limit resolution. It also enables TEM images and videos to be recorded with unprecedented time resolution, thereby providing a route to atomic-scale dynamics studies of complex systems. |
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