title: Direct imaging of transient molecular structures with ultrafast diffraction.
abstract: Ultrafast electron diffraction (UED) has been developed to study transient structures in complex chemical reactions initiated with femtosecond laser pulses. This direct imaging of reactions was achieved using our third-generation apparatus equipped with an electron pulse (1.07 +/- 0.27 picoseconds) source, a charge-coupled device camera, and a mass spectrometer. Two prototypical gas-phase reactions were studied: the nonconcerted elimination reaction of a haloethane, wherein the structure of the intermediate was determined, and the ring opening of a cyclic hydrocarbon containing no heavy atoms. These results demonstrate the vastly improved sensitivity, resolution, and versatility of UED for studying ultrafast structural dynamics in complex molecular systems.
authors.affiliation: Laboratory for Molecular Sciences, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ihee
authors.forename: V A
authors.initials: VA
authors.lastname: Lobastov
authors.forename: U M
authors.initials: UM
authors.lastname: Gomez
authors.forename: B M
authors.initials: BM
authors.lastname: Goodson
authors.forename: R
authors.initials: R
authors.lastname: Srinivasan
authors.forename: C Y
authors.initials: CY
authors.lastname: Ruan
authors.forename: A H
authors.initials: AH
authors.lastname: Zewail