Direct imaging of transient molecular structures with ultrafast diffraction.

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.

[1]  W. Leemans,et al.  Ultrafast Structural Dynamics in InSb Probed by Time-Resolved X-Ray Diffraction , 1999 .

[2]  H. Elsayed-Ali,et al.  Time-Resolved Reflection High-Energy Electron Diffraction Study of the Ge(111)-c(2×8)-(1×1) Phase Transition , 1999 .

[3]  H Ihee,et al.  Ultrafast electron diffraction and direct observation of transient structures in a chemical reaction. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[4]  V. Lobastov,et al.  Instrumentation for time-resolved electron diffraction spanning the time domain from microseconds to picoseconds , 1998 .

[5]  A. Zewail,et al.  Ultrafast electron diffraction: structures in dissociation dynamics of Fe(CO)5 , 1997 .

[6]  A. Zewail,et al.  Femtosecond Elimination Reaction Dynamics , 1997 .

[7]  Ahmed H. Zewail,et al.  Clocking transient chemical changes by ultrafast electron diffraction , 1997, Nature.

[8]  W. Fuß,et al.  Ultrafast dynamics of the photochemical ring opening of 1,3-cyclohexadiene studied by multiphoton ionization , 1996 .

[9]  Ahmed H. Zewail,et al.  Ultrafast Electron Diffraction. 5. Experimental Time Resolution and Applications , 1994 .

[10]  Lothar Schäfer,et al.  The stroboscopic gas electron diffraction method for investigation of time-resolved structural kinetics in photoexcitation processes , 1993 .

[11]  I. Mills,et al.  ASYM20: A Program for Force Constant and Normal Coordinate Calculations, with a Critical Review of the Theory Involved , 1993 .

[12]  A. Zewail,et al.  Ultrafast electron diffraction. Velocity mismatch and temporal resolution in crossed-beam experiments , 1993 .

[13]  S. Samdal,et al.  Conformational analysis. 15. 1,2-Dibromotetrafluoroethane and 1,2-diiodotetrafluoroethane. Electron diffraction investigations of the molecular structures, compositions, and anti-gauche energy and entropy differences , 1992 .

[14]  C. Bock,et al.  An ab initio structural and vibrational analysis of gauche,trans,trans- and gauche,cis,trans-hexa-1,3,5-trienes , 1992 .

[15]  G. Mourou,et al.  Time-Resolved Laser-Induced Phase Transformation in Aluminum , 1984, Topical Meeting on Ultrafast Phenomena.

[16]  J. Traynham,et al.  Radical brominations of alkyl bromides and the nature of .beta.-bromoalkyl radicals , 1984 .

[17]  V. Sundström,et al.  Femtochemistry and femtobiology : ultrafast reaction dynamics at atomic-scale resolution : Nobel Symposium 101, Björkborn, Sweden, September 9-12, 1996 , 1997 .

[18]  S. H. Bauer,et al.  Structures and conformations of the cyclohexadienes , 1969 .

[19]  S. J. Cyvin,et al.  The Single and Double Bonds between sp2-Hybridized Carbon Atoms, as Studied by the Gas Electron Diffraction Method. III. The Molecular Structure of 1,3,5-cis-Hexatriene. , 1968 .