BES - SLAC Group/Department Public Websites - Stanford University

FYO7 SLAC S CIENCE AND T ECHNOLOGY S ELF E VALUATION
interatomic potential even for the highly electronically excited system investigated
experimentally.
Imaging Atomic Structure and Dynamics with Ultrafast X-ray Scattering, K. J. Gaffney and H. N.
Chapman, Science, 316, 1444-1448 (2007)
We discussed recent advances in ultrafast x-ray science and x-ray coherent imaging, as well as
the tremendous opportunity the impending FEL facilities will have on these areas of science.
High Harmonic Generation for N2 and CO2 Beyond the Two Point Model, M. Gühr, B. K.
McFarland, J. P. Farrell and P. H. Bucksbaum, J. Phys. B: At. Mol. Opt. Phys., 40, 3745-3755
(2007)
We study how the electron orbital structure of molecules influences the generation of strong field
high harmonics of an intense laser. We compare simulations for N2 and CO2 to the predictions of
a simple model and present its applicability limits. Our results lead to a reinterpretation of
experimental studies in CO2.
Ultrafast Dynamics of Halogens in Rare Gas Solids, M. Gühr, M. Bargheer, M. Fushitani, T.
Kiljunen and N. Schwentner, Phys. Chem. Chem. Phys., 9, 779 - 801 (2007)
We present a complete study of the coherent electronic and vibrational wave packet dynamics of
small halogen molecules in rare gas crystals. In contrast to many other studies of solvated
molecules, we find long lasting electronic and vibrational coherences that are supported by the
cage structure. We use the long lasting coherences to excite double and triple wave packet
structures on the electronically excited state and get detailed information about the multiple-level
decoherence.
Imaging of Conical Intersections, M. Gühr, Bulletin of the American Physical Society, 52 (7),
J6.00011 (2007)
Conical intersections (CI) are crucially involved in light harvesting, primary visual processes,
DNA UV stabilization and atmospheric chemistry. A wave packet typically moves through the
intersection on a femtosecond time scale, demonstrating the need for ultrafast tools that are
sensitive to the electronic state change occurring in passing the CI. We propose a novel
femtosecond pump probe scheme based on HHG. A first pulse (pump) creates a molecular wave
packet on excited electronic surfaces, and the time delayed, high intensity probe pulse produces
HHG on the excited molecule as it moves through the CI region. We use the symmetry of the
electronic wave functions to detect the electronic state change in the CI via HHG. Furthermore,
we use two center interference effects in the HHG to determine the nuclear dynamics that is
accompanied by the CI passage. To demonstrate our scheme, we perform simple model
calculations on the triatomic molecule SO2, which will be ideally suited for experiments because
of its high UV excitation cross sections for pumping the wave packet to the CI region.
Carrier-density-dependent Lattice Stability in Sb, P. B. Hillyard, K. J. Gaffney, A. M. Lindenberg, S.
Engemann, R. A. Akre, J .Arthur, C. Blome, P. H. Bucksbaum, A. L. Cavalieri, A. Deb, R. W.
Falcone, D.M. Fritz, P. H. Fuoss, J. Hajdu, P. Krejcik, J. Larsson, S. H. Lee, D. Meyer, A. J., Nelson,
R. Pahl, D. A. Reis, J. Rudati, D. P. Siddons, K.Sokolowski-Tinten, D.von der Linde and J. B.
Hastings, Phys. Rev. Lett., 98, 125501 (2007)
We experimentally identified the carrier dependent onset of interatomic potential softening and
the carrier dependent onset of interatomic potential inversion.
Ultrafast Electron Pulses From a Tungsten Tip Triggered By Low-Power Femtosecond Laser Pulses,
P. Hommelhoff, C. Kealhofer and M. A. Kasevich, Phys. Rev. Lett., 97, 247402 (2006)
We present an experimental and numerical study of electron emission from a sharp tungsten tip
triggered by sub-8-fs low-power laser pulses. This process is nonlinear in the laser electric field,
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