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Clocking transient chemical changes by ultrafast electron diffraction

Williamson, J. Charles and Cao, Jianming and Ihee, Hyotcherl and Frey, Hans and Zewail, Ahmed H. (1997) Clocking transient chemical changes by ultrafast electron diffraction. Nature, 386 (6621). pp. 159-162. ISSN 0028-0836. doi:10.1038/386159a0.

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With the advent of femtosecond (fs) time resolution in spectroscopic experiments, it is now possible to study the evolution of nuclear motions in chemical and photobiochemical reactions. In general, the reaction is clocked by an initial fs laser pulse (which establishes a zero of time) and the dynamics are probed by a second fs pulse; the detection methods include conventional and photoelectron spectroscopy and mass spectrometry. Replacing the probe laser with electron pulses offers a means for imaging ultrafast structural changes with diffraction techniques, which should permit the study of molecular systems of greater complexity (such as biomolecules). On such timescales, observation of chemical changes using electron scattering is non-trivial, because space-charge effects broaden the electron pulse width and because temporal overlap of the (clocking) photon pulse and the (probe) electron pulse must be established. Here we report the detection of transient chemical change during molecular dissociation using ultrafast electron diffraction. We are able to detect a change in the scattered electron beam with the zero of time established unambiguously and the timing of the changes clocked in situ. This ability to clock changes in scattering is essential to studies of the dynamics of molecular structures.

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Additional Information:© 1997 Nature Publishing Group. Received 8 October 1996; accepted 21 January 1997. We thank S. Preuss for his help in the construction and testing of the experimental apparatus, and H. Elsayed-Ali for providing us with part of the design of the electron gun.
Issue or Number:6621
Record Number:CaltechAUTHORS:20150617-104644558
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Official Citation:Clocking transient chemical changes by ultrafast electron diffraction 159 J. Charles Williamson, Jianming Cao, Hyotcherl Ihee, Hans Frey & Ahmed H. Zewail doi:10.1038/386159a0
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58318
Deposited By: Ruth Sustaita
Deposited On:17 Jun 2015 18:46
Last Modified:10 Nov 2021 22:03

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