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Author(s): A. Cavalleri (corresponding author) [1, 2]; S. Wall [1]; C. Simpson [1]; E. Statz [3]; D. W. Ward [3]; K. A. Nelson [3]; M. Rini [4]; R. W. Schoenlein [...]

Femtosecond synchrotron pulses were generated directly from an electron storage ring. An ultrashort laser pulse was used to modulate the energy of electrons within a 100-femtosecond slice of the stored 30-picosecond electron bunch. The energy-modulated electrons were spatially separated from the long bunch and used to generate ~300-femtosecond synchrotron pulses at a bendmagnet beamline, with a spectral range from infrared to x-ray wavelengths. The same technique can be used to generate ~100-femtosecond x-ray pulses of substantially higher flux and brightness with an undulator. Such synchrotron-based femtosecond x-ray sources offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter., An important scientific frontier is the application of x-ray pulses to investigate ultrafast structural dynamics (atomic motion and rearrangement) associated with phase transitions in solids, chemical reactions, and rapid biological [...]

Ever since the conversion of the 11-cis retinal chromophore to its all- trans form in rhodopsin was identified as the primary photochemical event in vision (1), experimentalists and theoreticians have tried to unravel the molecular details of this process. The high quantum yield of 0.65 (ref. 2), the production of the primary ground-state rhodopsin photoproduct within a mere 200 fs (refs 3-7), and the storage of considerable energy in the first stable bathorhodopsin intermediate (8) all suggest an unusually fast and efficient photoactivated one-way reaction (9). Rhodopsin's unique reactivity is generally attributed to a conical intersection between the potential energy surfaces of the ground and excited electronic states (10,11) enabling the efficient and ultrafast conversion of photon energy into chemical energy (12-16). But obtaining direct experimental evidence for the involvement of a conical intersection is challenging: the energy gap between the electronic states of the reacting molecule changes significantly over an ultrashort timescale, which calls for observational methods that combine high temporal resolution with a broad spectral observation window. Here we show that ultrafast optical spectroscopy with sub-20-fs time resolution and spectral coverage from the visible to the near-infrared allows us to follow the dynamics leading to the conical intersection in rhodopsin isomerization. We track coherent wave-packet motion from the photoexcited Franck-Condon region to the photoproduct by monitoring the loss of reactant emission and the subsequent appearance of photoproduct absorption, and find excellent agreement between the experimental observations and molecular dynamics calculations that involve a true electronic state crossing. Taken together, these findings constitute the most compelling evidence to date for the existence and importance of conical intersections in visual photochemistry., We initiated the photoisomerization reaction in the retinal chromophore of purified rhodopsin by 10-fs 500-nm pump pulses resonant with the ground-state absorption. The photoinduced dynamics were then probed by delayed [...]

Tracing the transient atomic motions that lie at the heart of chemical reactions requires high-resolution multidimensional structural information on the timescale of molecular vibrations, which commonly range from 10 fs [...]

Comprehensive knowledge of the dynamic behaviour of electron' in condensed-matter systems is pertinent to the development of many modern technologies, such as semiconductor and molecular electronics, optoelectronics, information processing and [...]

Author(s): Henry N. Chapman (corresponding author) [1, 2]; Stefan P. Hau-Riege [1]; Michael J. Bogan [1]; Saša Bajt [1]; Anton Barty [1]; Sébastien Boutet [1, 3, 4]; Stefano Marchesini [1, [...]

Author(s): C. G. R. Geddes [1, 2]; Cs. Toth [1]; J. van Tilborg [1, 3]; E. Esarey [1]; C. B. Schroeder [1]; D. Bruhwiler [4]; C. Nieter [4]; J. Cary [...]

Author(s): Muneaki Hase [1]; Masahiro Kitajima [1]; Anca Monia Constantinescu [2]; Hrvoje Petek (corresponding author) [2] The concept of quasiparticles in solid-state physics is an extremely powerful tool for describing [...]

Author(s): M. Drescher (corresponding author) [1, 2]; M. Hentschel [1]; R. Kienberger [1]; M. Uiberacker [1]; V. Yakovlev [1]; A. Scrinzi [1]; Th. Westerwalbesloh [2]; U. Kleineberg [2]; U. Heinzmann [...]

Author(s): M. F. DeCamp (corresponding author) [1]; D. A. Reis [1]; P. H. Bucksbaum [1]; B. Adams [2]; J. M. Caraher [1]; R. Clarke [1]; C. W. S. Conover [3]; [...]

Author(s): Ferenc Krausz (corresponding author) [1]; Christian Spielmann (corresponding author) [1] Since their discovery some 100 years ago by Wilhelm Röntgen [1], X-rays have found important uses in hospitals, laboratories [...]

The heyday of information theory in psychology occurred sometime during the 1950s. Inspired by the seminal work of Shannon (1948), hundreds of articles during this period attempted to show that [...]

Author(s): R. Bartels [1]; S. Backus [1]; E. Zeek [1]; L. Misoguti [1]; G. Vdovin [2]; I. P. Christov [3]; M. M. Murnane [1]; H. C. Kapteyn (corresponding author) [1] [...]

Author(s): Andrea Cavalleri [1] On page 676 of this issue [1], Chapman et al . demonstrate how coherent, ultrafast X-ray pulses from a free-electron laser [2] can be used to [...]