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Oriented Ensembles in Ultrafast Electron Diffraction

Baskin, J. Spencer and Zewail, Ahmed H. (2006) Oriented Ensembles in Ultrafast Electron Diffraction. ChemPhysChem, 7 (7). pp. 1562-1574. ISSN 1439-4235.

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Electron scattering expressions are presented which are applicable to very general conditions of implementation of anisotropic ultrafast electron diffraction (UED) experiments on the femto- and picosecond time scale. “Magic angle” methods for extracting from the experimental diffraction patterns both the isotropic scalar contribution (population dynamics) and the angular (orientation-dependent) contribution are described. To achieve this result, the molecular scattering intensity is given as an expansion in terms of the moments of the transition-dipole distribution created by the linearly polarized excitation laser pulse. The isotropic component (n=0 moment) depends only on population and scalar internuclear separations, and the higher moments reflect bond angles and evolve in time due to rotational motion of the molecules. This clear analytical separation facilitates assessment of the role of experimental variables in determining the influence of anisotropic orientational distributions of the molecular ensembles on the measured diffraction patterns. Practical procedures to separate the isotropic and anisotropic components of experimental data are evaluated and demonstrated with application to reactions. The influence of vectorial properties (bond angles and rotational dynamics) on the anisotropic component adds a new dimension to UED, arising through the imposition of spatial order on otherwise randomly oriented ensembles.

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Additional Information:© 2006 Wiley-VCH Verlag GmbH & Co. Received: March 7, 2006. Published online on June 21, 2006. This research was supported by the National Science Foundation and the Air Force Office of Scientific Research.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Subject Keywords:femtochemistry; gas-phase reactions; molecular structures; structural dynamics; ultrafast electron diffraction
Issue or Number:7
Record Number:CaltechAUTHORS:20160816-122129206
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Official Citation:Baskin, J. S. and Zewail, A. H. (2006), Oriented Ensembles in Ultrafast Electron Diffraction. ChemPhysChem, 7: 1562–1574. doi: 10.1002/cphc.200600133
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69669
Deposited By: Ruth Sustaita
Deposited On:16 Aug 2016 20:49
Last Modified:03 Oct 2019 10:24

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