All Posters by Session

Thursday

• T01: "Streaking of shake-up ionization in helium"
  Johannes Feist, Andreas Kaltenbäck, Stefan Nagele, Renate Pazourek, Emil Persson, Barry I. Schneider, Lee A. Collins, Joachim Burgdörfer We investigate whether an apparent ``time delay'' between electrons ionized by an attosecond XUV pulse with and without shake-up excitation of the remaining ion can be extracted using XUV-IR streaking setups. To do so, we solve the full Schrödinger equation for the helium atom including all correlation effects. We discuss whether a time delay extracted from the streaking spectra corresponds to a ``real'' time delay or is induced by other effects, such as the influence of the IR field on the ionization process.
• T02: "Elliptically polarized high-order harmonics from aligned molecules within the strong-field approximation"
  Adam Etches, Christian Bruun Madsen, Lars Bojer Madsen A correction term is introduced in the stationary-point analysis on high-order harmonic generation (HHG) from aligned molecules. Arising from a multi-centre expansion of the electron wave function, this term brings our numerical calculations of the Lewenstein model into qualitative agreement with recent experiments.
• T03: "High harmonics generation using long wavelengths: scaling and scaled systems"
  Gilles Doumy, Anne Marie March, Erik Power, Jonathan Wheeler, Chris Roedig, Emily Sistrunk, Fabrice Catoire, Karl Krushelnick, Pierre Agostini, Louis DiMauro Long wavelength lasers have started to become ubiquitous in studies of high harmonics generation, due to their attractive scaling properties (cutoff extension, better synchronization for shorter pulses). They also enable studies where the whole interaction is scaled compared to the usual situation using 800nm light. I will present both results that verified the wavelength scaling and a complete temporal characterization of the emission in a scaled Cesium 3.6micron system using Cross-correlation frequency resolved optical gating (XFROG).
• T04: "Modeling Attosecond Pulse Formation in Strongly Ionized Gaseous Media"
  V. Tosa,1, K. Kovacs, R. Velotta, C. Altucci, K. T. Kim, and C. H. Nam We present the results obtained in modeling single attosecond pulse (SAP) as well as attosecond pulse trains (APT) formation as a result of femtosecond laser pulse interaction with rare gas atoms. A non-adiabatic model is used for solving the laser and harmonic field propagation, while strong field approximation is used to calculate the single dipole response. Quantum trajectories of the electron are generated and their phases are used in a time-dependent phase matching analysis. The role of the propagation can be beneficial in SAP generation as it contributes to the elimination of spurious bursts. APT characteristics will bear the signature of the distorted laser field, which will generate less, shorter and shifted to earlier time wagons.
• T05: "Benchmark experiment on H3+ in intense ultrashort laser pulses"
  J. McKenna, A. M. Sayler, B. Gaire, Nora G. Johnson, K. D. Carnes, B. D. Esry and I. Ben-Itzhak Using coincidence 3D momentum imaging we have probed, for the first time, the fragmentation dynamics of H3+ and its isotopologues in intense ultrashort laser pulses. As the simplest polyatomic molecule, these measurements on H3+ can serve as a benchmark for future theoretical calculations.
• T06: "Ultrafast high-harmonic imaging of a chemical reaction"
  H. J. W¨orner, J. B. Bertrand, P. B. Corkum and D. M. Villeneuve High-harmonic generation in aligned molecules provides information about their electronic structure and ionization continuum within a fraction of a laser cycle. We exploit the ultrahigh time resolution to experimentally observe a chemical reaction of fixed-in-space molecules. We non-adiabatically align Br2 molecules, launch a photodissociation wave packet and measure the high harmonic yield as a function of time delay and angle between the molecular axis and the polarization of the generating laser field. We develop an interferometric technique to extract the harmonic dipole and phase of the excited state along the photodissociation coordinate. This provides the complete information required for the dynamic tomographic imaging of the chemical reaction.
• T07: "Attosecond Electron Interferometry"
  K. Klünder, M. Swoboda, M. Gisselbrecht, M. J. Dahlström, P. Johnsson, T. Remetter, J. Mauritsson, A. L'Huillier We present two different interferometric pump-probe experiments aiming to access state specific phase information after attosecond pulse excitation. The common idea is that when creating the wave packet we introduce simultaneously a reference that allows us to measure the phase evolution. In the first experiment we use isolated attosecond pulses to characterize ultrafast bound electron dynamics. While in the second we apply attosecond pulse trains in a RABITT measurement to access the phase induced by a resonant bound state in a two-photon-ionization process.
• T08: "Electron Wavepacket Interferences pointing to Holographic Imaging with Few Cycle Laser Pulses"
  R. Gopal, A. Rudenko, K. Simeonidis, K.-U. Kühnel, M. Kurka, C. D Schröter, O. Herrwerth, Th.Uphues, M. Schultze, E. Goulielmakis, M. Uiberacker, D. Bauer, M. Lezius, R. Moshammer, M. F. Kling, J. Ullrich Three-dimensional (3D) electron (and ion) momentum (P) spectra have been recorded for carrier-envelope-phase (CEP) stabilized few-cycle (~5 fs), intense (~0.4 PW/cm2) laser pulses (740 nm) impinging on He using a reaction microscope. Preferential emission of low-energy electrons (Ee < 15 eV) to either hemisphere is observed as a function of the CEP. Clear interference patterns emerge in P-space at CEPs with maximum asymmetry, interpreted as holographic images of re-scattered electron wavepackets by means of a simple model and in line with previous theoretical predictions.
• T09: "Asymmetric dissociation of H2 and D2 by a two-color laser field"
  D. Ray, S. De, H. Mashiko, I. Znakovskaya, F. He, U. Thumm, G.G.Paulus, M. Kling, I. Litvinyuk, and C.L. Cocke Two-color (800 nm and 400 nm) short (45 fs) linearly polarized pulses are used to ionize and dissociate H2(D2) into a neutral hydrogen (deuterium) atom and a proton(deuteron). The yields and energies of the ions are measured left and right along the polarization vector. As the relative phase of the two colors is varied, strong yield asymmetries are found in the ion energy regions corresponding to bond softening, above-threshold dissociation and rescattering. A model based on the dynamic coupling by the laser field of the gerade and ungerade states in the molecular ion accounts for many of the observed features.
• T10: "Intensity dependence of strong field double ionization mechanisms of diatomic molecules: from field-assisted electron recollision to recollision-assisted field ionization"
  Agapi Emmanouilidou Given the state of the art in computational capabilities addressing the double ionization of strongly driven diatomic molecules with three-dimensional (3-d) firstprinciple techniques, namely quantum mechanical ones, is an immense task. We study the correlated electron dynamics in the double ionization of diatomic molecules with “frozen” nuclei in the non-sequential regime as a function of the intensity of the laser pulse.
• T11: "Time-resolved core-hole decay and sideband structure in laser-assisted photoemission from metal surfaces"
  C.-H. Zhang, U. Thumm We calculate the photoelectron and Auger electron sideband spectra and the ¯rst sideband intensities from adsorbate-covered metal surfaces
• T12: "Time-resolved Coulomb explosion imaging of CO ultrafast dynamics using fewcycle IR and EUV laser pulses"
  A. S. Alnaser, I. Bocharova, K. Singh, C. Wei, M. Kling, C. L. Cocke, I. V. Litvinyuk We have used few-cycle IR and EUV laser pulses in pump-probe arrangement to trace out the dissociation pathways in CO when exploded by strong laser fields. We present two preliminary sets of data of different pump pulses. In these sets, different excited state of CO cations are populated using (< 10 fs) IR, and EUV pulses respectively. We followed the time evolution of these states using the time-resolved Coulomb explosion imaging technique. We compare the time evolution of IR- and EUV-induced excited states by measuring the KER of the fragment ions as a function of the time delay between the pump and the IR probe pulse.
• T13: "Ultrashort IR-visible- and VUV-pulse generation for attosecond pump-probe experiments on atoms and molecules using a reaction microscope"
  K. Simeonidis, R. Gopal, H. Rietz, A. Sperl and J. Ullrich The status of the new attosecond beamline at Max-Planck-Institut fuer Kernphysik (MPIK), Heidelberg, and ongoing experiments is reported. The beamline is designed for detailed investigation of the electronic response in atoms and molecules by combining a versatile HHG-source with a compact reaction microscope. Ultrashort laser pulses down to 4~fs generatetd by a novel pulse compression setup utilizing filamentation are applied to produce isolated attosecond pulses.
• T14: "Magnetic-bottle electron energy spectrometer for measuring 25 as pulses"
  Kun Zhao, Chao Wang, Ximao Feng, Steve Gilbertson, Sabih D. Khan, and Zenghu Chang Non-uniform field in a magnetic-bottle electron energy spectrometer (MBEES) was simulated with finite-element software. The result showed that a field close to 1T may be obtained at the interaction region with a carefully designed NdFeB permanent magnet and soft iron pole piece. This field meets the requirement for 25as pulse duration measurement.
• T15: "Interferometric Delay Control in Attosecond Streaking Experiments"
  Michael Chini, He Wang, Hiroki Mashiko, Shouyuan Chen, Chenxia Yun, Steve Gilbertson, Zenghu Chang Attosecond streaking experiments suffer from interferometric instability due to fluctuating environmental conditions as well as mechanical vibration of the optical elements and vacuum pumps. Such instability causes the delay between the attosecond pump and infrared streaking pulses to drift. Here, we present a novel method for stabilizing the interferometer path length difference and controlling the delay. Using this scheme, the streaked spectrogram of a single attosecond pulse is measured by velocity map imaging.
• T16: "Ab Initio Modeling of Attosecond Streaking Measurements"
  M. Korbman, Y. Komninos, T. Mercouris, C.A. Nicolaides, F. Krausz, V.S. Yakovlev We model attosecond streaking measurements beyond the single-active-electron approximation. With the aid of the state-specific-expansion approach, we perform ab-initio many-electron simulations, where an N-electron wave function is described within a basis of physically relevant atomic and ionic states.
• T17 O08: "Attosecond Hard X-Ray Scattering Spectroscopy"
  G. L. Yudin, D. I. Bondar, S. Patchkovskii, P. B. Corkum, A. D. Bandrauk We formulate an analytic, semi-relativistic theory of laser-assisted attosecond Compton scattering by a weakly bound electron. We (i) present the evidence of the feasibility of measuring the ground-state electron momentum density in the attosecond regime and (ii) investigate the attosecond Compton streak camera and spectral phase interferometry - proposing two new methods of measuring the duration of a hard x-ray pulse without fundamental restrictions on the measurement accuracy.
• T18: "Phase-matching of high-order harmonic generation in a semi-infinite gas cell geometry"
  Daniel S. Steingrube, Tobias Vockerodt, Emilia Schulz, Uwe Morgner, and Milutin Kovacev Phase-matching of high-order harmonic generation in a semi-infinite gas cell geometry is investigated. A systematic study of experimental phase-matching conditions with variation of pressure and focus positions is performed for different focal lengths and in different rare gases. These results are compared to phase-matching simulations.
• T19: "Wavelength Scaling of High Harmonic Generation Efficiency"
  A. D. Shiner, C. Trallero-Herrero, N. Kajumba, H.-C Bandulet, D. Comtois, F. Légaré, M. Gigèure, J-C. Kieffer, P. B. Corkum, D. M. Villeneuve We present a measurement of the dependence of xuv yield, from high harmonic generation, on laser wavelength. Parameters important to phase matching such as focusing geometry and mode quality were controlled and the measured HHG yield was normalized to the number of emitters in the interaction volume. We find that XUV yield scales as λ-6.3±1.1 in Xe and λ-6.5±1.3 in Kr at a constant laser intensity.
• T20: "Femtosecond enhancement cavities for high repetition rate HHG"
  D. C. Yost, Jun Ye High repetition rate high harmonic generation (HHG) has great potential as a source of XUV radiation with exceptional frequency resolution . We present progress in our ability to efficiently create this radiation within a passive optical cavity. This has enabled new tests of the temporal coherence of the harmonic radiation as well as fundamental studies of quantum paths in below-threshold harmonic generation.
• T21: "Highly stable, few-cycle, 2.2-μm optical parametric chirped pulse amplifier"
  Shu-Wei Huang, Jeffrey Moses, Kyung-Han Hong, Edilson L. Falcão-Filho, Andrew Benedick, Jeremy Bolger, Benjamin Eggleton, Franz X. Kärtner We demonstrate a 10-GW peak power, 3-optical-cycle, CEP-stabilized, 2.2-μm OPCPA with 1-kHz repetition rate. Implementation of superfluorescence suppression techniques enables rms energy and intensity fluctuations of only 1.5% and 0.8%, respectively.
• T22: "Temperature feedback control for long-term carrier-envelope phase locking"
  Shouyuan Chen, Chenxia Yun, He Wang, Michael Chini, and Zenghu Chang We report a double feedback loop to improve the long-term carrier-envelope phase stabilization of a chirped mirror based oscillator. By combining the temperature control of the Ti: Sapphire crystal and conventionalpump power modulation, the carrier-envelope offset frequency fceo can be locked for 34 hours, which is many timeslonger than the stabilization time using pump power modulation only.
• T23: "Fractional Instability of a Phase Stabilized Carbon Nanotube Fiber Laser Frequency Comb"
  Jinkang Lim, Kevin Knabe, Yishan Wang, Rodrigo Amezcua-Correa, François Couny, Philip S. Light, Fetah Benabid, Jonathan C. Knight, Kristan L. Corwin, Jeffrey W. Nicholson, Brian R. Washburn A 167 MHz repetition frequency fiber ring laser employing single walled carbon nanotubes mode-locker is phase-stabilized for the first time. The stability of the frequency comb generated by this laser has been measured by comparing it with a figure eight laser (F8L) and by beating it against a 1532 nm CW laser stabilized to a ?1+?3 overtone transition of an acetylene-filled kagome photonic crystal fiber reference. The result shows the stability of comb to be ~10-11 in 1 s averaging time.
• T24: "Coupling between Energy and Carrier-Envelope Phase in Hollow-Core Fiber based f-to-2f Interferometers"
  He Wang, Michael Chini, Eric Moon, Hiroki Mashiko, and Zenghu Chang The coupling coefficient between carrier-envelope phase and laser pulse energy is measured for white-light generation from a hollow-core fiber. It is determined that 1% fluctuation in laser energy gives a phase shift of 128 mrad.
• T25: "An isolated short attosecond pulse produced by using intense few-cycle chirped laser and an ultraviolet attosecond pulse"
  Xiao-Xin Zhou, Song-Feng Zhao, Peng-Cheng Li, Zhangjin Chen An efficient method to generate a short attosecond(as) pulse is presented by using an intense few-cycle chirped infrared(IR) laser in combination with an ultraviolet (UV) attosecond pulse. We show that high-order harmonic generation (HHG) plateau near the cutoff is enhanced by one order of magnitude compared with the chirped laser case and the HHG supercontinuum spectrum is generated by adding a UV attosecond pulse to the few-cycle chirped IR laser at a proper time. By enhancing the long quantum path and suppressing the short one corresponding to one major return, an isolated 57-as pulse with a bandwidth of 62 eV is obtained directly.
• T26: "Multiple Ionic Channel Formulation for Strong Field Single Ionization of Multielectron Targets"
  Michael Spanner, Serguei Patchkovskii, Julien Bertrand, and Hans Jakob Worner We present a novel approach to calculating strong ¯eld ionization dynamics of multielectron molecular targets. Adopting a multielectron wavefunction ansatz based on ¯eld-free ab initio neutral and ionic multielectron states, a set of coupled time-dependent single-particle SchrÄodinger equations describing the neutral amplitude and continuum electron are constructed. These equations, amenable to direct numerical solution or further analytical treatment, allow one to study multielectron e®ects during strong ¯eld ionization, recollision, and high harmonicgeneration.
• T27: "Ultrafast Molecular Dynamics Probed Using Strong Field Ionization"
  Wen Li; Vandana Sharma; Craig Hogle; Agnieszka Jaron-Becker; Andreas Becker; Henry Kapteyn, Margaret Murnane We report preliminary measurements using strong field ionization to monitor the photodissociation of bromine molecules. The time dependent kinetic energy release (KER) of bromine cations (Br+) was used to identify the molecular cation states (Br2+),which contribute to the production of Br+. We observe a strong angular dependence of the Br+ yield, representing the shape of the ionizing molecular orbital. The time evolution of the angular distribution of Br+ was also obtained. This is the first experimental demonstration of using strong field ionization to monitor orbital rearrangement during a chemical reaction.
• T28: "Single Molecule Laser Induced Nuclear Fusion, LINF, In Superintense Laser Fields"
  Andre D. Bandrauk, Gennady K. Paramonov We show in the present study the importance of Carrier Envelope Phase of current and future ultrashort superintense laser pulses in controlling recollision processes in muonic molecular systems.
• T29 O06: "Counterintuitive angular shifts in the photoelectron momentum distribution for atoms in strong few-cycle circularly laser pulses"
  C. P. J. Martiny, M. Abu-samha, L. B. Madsen We have recently developed a method for solving the time-dependent Schro127 odinger equation for a diatomic molecule (atom) interacting with a strong few-cycle elliptically polarized laser pulse. Here we present the first fully ab initio calculations of the photoelectron momentum distributions for a circularly polarized laser pulse interacting with an atom. Furthermore, we provide a precise quantum mechanical explanation of counterintuitive shifts in the dominant direction of electron ejection, observed in a recent experiment (P. Eckle et.al. Science 322, 1525 (2008)). Our results underline the importance of including both the laser field and the Coulomb interaction in the description.
• T30: "Manipulating the torsion of molecules by strong laser pulses"
  C. B. Madsen, L. B. Madsen, S. S. Viftrup, M. P. Johansson, T. B. Poulsen, L. Holmegaard, V. Kumarappan, K. A. Jørgensen, H. Stapelfeldt In recent years the manipulation of molecules by strong laser pulses has attracted much attention. Non-resonant laser fields apply torques on molecules, due to the interaction between the induced dipole moment and the laser field itself. This has proven very useful for controlling both external and internal degrees of freedom of molecules. We extend the use of strong non-resonant laser fields to manipulation of the torsion in a molecule. Specifically, we consider the laser induced dynamics of the two phenyl rings of a biphenyl molecule.
• T31: "The onset of asymmetry in electron angular distributions for dissociative photoionization of H2 by ultrashort xuv laser pulses"
  J. F. Perez-Torres, F. Morales, J. L. Sanz-Vicario and F. Martýn A method to compute angular distributions for electrons ejected from fixed-in-space molecular hydrogen when exposed to ultrashort xuv laser pulses is proposed based on the ab initio solution of the time-dependent Schr¨odinger equation. This method allows for a temporal picture of the origin of the asymmetry in the electron angular ejection that arise due to the interference of the two symmetric dissociative ionization channels (1sg and 2pu) in which molecular autoionization states decay after photon absorption.
• T32: "Electron localization following attosecond molecular photionization"
  F. Kelkensberg, G. Sansone, M.F. Kling, W. Siu, O. Ghafur, P. Johnsson, M. Swoboda, E. Benedetti, F. Ferrari, F. Lépine, S. Zherebtsov, I. Znakovskaya, M. Yu. Ivanov, J.F. Pérez, F. Morales, J.L. Sanz-Vicario, F. Martin, M. Nisoli, M.J.J. Vrakking Observation and control of electron dynamics on attosecond timescales are the main driving forces behind the recent emergence of attosecond science. In this experiment an isolated attosecond laser pulse ionizes D2. and part of the ionized molecules dissociate. Interaction of these dissociating wave packets with a moderately strong IR field localizes the electron on one of the D+ ions. By varying the delay between the XUV pulse and the few-cycle IR pulse, the localization is controlled with attosecond resolution. A detailed comparison between the experiment and a full-dimensional model is presented.
• T33: "Time-Resolved Molecular Fragmentation at FLASH"
  Jiang, Rudenko, Kurka, Kühnel, Toppin, Herrwerth, Lezius, Kling, Foucar, Schöffler, Cole, Ullrich, Neumann, Dörner, Pérez-Torres, Plésiat, Martín, Cassimi, Düsterer, Treusch, Gensch, Schröter, Moshammer, Ullrich Multiple ionization and fragmentation of D2 and N2 induced by absorption of few photons have been explored in pump-probe measurements at the free electron laser at Hamburg. Photoionization of aligned N2+ ions, produced in sequential step, is explored by inspecting the kinetic energy releases and the fragment-ion angular distributions as function of the pump-probe delay time.
• T34: "Intense-Field Ionization of Cyclic Hydrocarbon Molecules Measured with Spatial Resolution of Focal Ion Distributions"
  Tim Scarborough, James Strohaber, David Foote, and Cornelis Uiterwaal We present experimental results of fully three-dimensionally resolved ion yields for benzene and benzene-like molecules, including some heterocyclic compounds. Full spatial resolution of the ion yields allows circumvention of the “volume effect”, in which ions are collected from the entire laser focus at a variety of intensities. As a result of avoiding this effect, our ion yields very closely resemble the true ionization probability, and have allowed us to clearly measure resonance-enhanced multiphoton ionization processes (REMPI).
• T35 O09: "Electron localization in molecular fragmentation with CEP stabilized laser pulses"
  Bettina Fischer, Manuel Kremer, Bernold Feuerstein, Vitor L.B. de Jesus, Artem Rudenko, Claus Dieter Schröter, Robert Moshammer, Joachim Ullrich Fully differential data on dissociating H2 molecules in ultrashort (~6 fs), linearly polarized, intense (~0,4 PWcm-2) laser pulses with stabilized carrier-envelope-phase (CEP) have been measured using a reaction microscope. Depend-ing on the CEP of the laser pulses we see a clear asymmetry in the emission direction of the created protons. Con-trary to earlier measurements by Kling et al. [1] we observe the largest asymmetry in a kinetic energy release (KER) range between 0-3 eV. This excludes the recollision mechanism suggested in [1] and requires another explanation.
• T36: "Vibrationally cold CO2+ probed by intense femtosecond laser pulses"
  J. McKenna, A. M. Sayler, B. Gaire, Nora G. Johnson, M. Zohrabi, F. Anis, U. Lev, K. D. Carnes, B. D. Esry, and I. Ben-Itzhak Using a novel approach, we produce a vibrationally cold CO2+ beam for study in an intense ultrashort laser field. We observe perpendicular dissociation of the simple two-level CO2+ v=0 ion, and above-threshold dissociation peaks spaced by the photon energy.
• T37: "Electron release dynamics in double ionization of Ar and Ne by elliptically polarized laser pulses"
  Adrian Pfeiffer, C. Cirelli, M. Smolarski, R. Dörner, U. Keller Elliptically polarized laser pulses are suitable to investigate double ionization isolated from electron recollision effects. For Ar and Ne we observe a characteristic transition in the momentum spectra of the doubly charged ions when the laser peak intensity is varied across the over-barrier intensity of the second ionization level. We find a qualitative agreement of our data with a simulation based on sequential double ionization and interpret our observation as a sensitive fingerprint of depletion.
• T38 O03: "Auger decay in krypton induced by attosecond pulse trains and twin pulses"
  Christian Buth, Kenneth J. Schafer Using attoscience, we study the electron correlations responsible for Auger decay in krypton atoms. The Auger decay is induced by a pulse train or a twin pulse composed of subpulses of attosecond duration. During the Auger decay an optical dressing laser may be present. Interference effects between the ejected Auger electron wave packets are predicted.
• T39: "Photoelectron emission from atoms by ultra-short pulses: Impulse Coulomb-Volkov description"
  M.S. Gravielle, D.G. Arbó, J.E. Miraglia Ionization of atomic targets produced by ultra-short laser pulses is studied within a distorted-wave formalism. We introduce the Impulse Coulomb-Volkov (ICV) approximation, which makes use of the Volkov phase to describe the action of the electromagnetic field on both the initial and final channels. Here photoelectron emission from hydrogen is used as a benchmark for the theory, comparing the results to values derived from the numerical solution of the time-dependent Schrödinger equation (TDSE). We found the ICV method represents an improvement over the CV approach for laser frequencies lower than the initial electronic energy.
• T40: "Electron emission from metal surfaces by ultra-short pulses"
  M. N. Faraggi, I. Aldazabal, M. S. Gravielle, A. Arnau, V. M. Silkin We study electron emission spectra produced by the grazing incidence of ultra-short laser pulses on metal surfaces. To describe this process we introduce a distorted-wave approach, based on a simple description of the solid, which include the main features of the process, taking into account the contribution of the induced potential. The method is applied to evaluate photoemission from the valence band of Al(111), considering different frequencies and durations of the pulse. The results so obtained are contrasted with the numerical solution to the time-dependent Schrödinger equation (TDSE), finding a very good agreement through the whole energetic range.
• T41: "Interference effects in laser assisted photo-ionization of atoms"
  Pablo A. Macri, Denise Bendersky Interference effects in laser assisted photoionization of atoms by an XUV pulse is considered by means of the Coulomb Volkov approximation. We find that the interference pattern can be related with the time delay between the laser and the XUV pulse.
• T42: "Acceleration of neutral atoms in intense short laser"
  U. Eichmann, T. Nubbemeyer, H. Rottke , and W. Sandner We report experimental results on a new acceleration mechanisms for neutral atoms in a strong laser field (I~=~10$^{16}$W~cm$^{-2}$). A simple model can explain the observed accelerations with magnitudes as high as 10$^{14}$ times Earth's gravitational acceleration.
• T43: "Carrier-envelope phase stabilization of a high-power regenerative amplifier"
  Fraser Turner, Andrei Naumov, Chengquan Li, Alan Fry We present the results of the carrier-envelope phase stabilization of the commercially available high-power regenerative amplifier. We show the comparison between in-loop and out-of-loop phase noise measurements and discuss the effect of the Pockels cells on the carrier-envelope phase stability.
• T44p: " Effects of Phase-Matching on High Harmonic Generation from Aligned N2 "
  B.A. Sickmiller, R.R. Jones We have used two time-delayed laser pulses to examine high harmonic generation from transiently aligned, room temperature N2 molecules in a hollow-core waveguide. The extended interaction length in the waveguide allows us to identify alignment-dependent propagation effects which mask the single molecule response. In particular, we observe a reversal in the harmonic efficiency from parallel to perpendicular alignment. This reversal depends on laser intensity and harmonic order. Simulations indicate that it can be attributed to the alignment-dependence of the tunneling ionization rate and the concomitant modification of the phase-matching conditions due to the changes in the free-electron density in the fiber.
• T45p: " Probing electron localization in laser-driven diatomic molecules by attosecond pulses "
  Jun Bao, Zengxiu Zhao We explore the possibility of using attosecond pulses to probe electronic dynamics of molecules driven by a laser field in real time. Taking advantage of the interference in the photoionization process, we show that the information of the electronic dynamics, particularly the electron localization can be imaged with attosecond pulses. We expect the same technique can be used to imaging atoms or molecules polarized by laser fields.

Friday

• F01: "Extending upper limit of laser pulse duration for generating single attosecond pulses"
  Ximao Feng, Steve Gilbertson, Hiroki Mashiko, He Wang, Sabih D. Khan, Michael Chini, Zenghu Chang We propose and demonstrate a technique called generalized double optical gating for generating isolate attosecond pulses with 20 fs lasers. These pulses are measured to be 260 attoseconds by reconstructing the streaked photoelectron spectrogram
• F02: "Electron Localization and Multiple Ionization Bursts in H2+ within a Half Cycle of Near-Infrared Laser Light"
  Norio Takemoto, Andreas Becker We found by numerical simulations that H2+ irradiated by intense near-infrared laser light shows multiple bursts of ionization current within a half cycle of the electric field oscillation, in contrast to the intuition given by the quasi-static tunneling ionization picture. We attribute the origin of the multiple bursts to the dynamical localization of the electron at one of the nuclei on the sub-laser-cycle time-scale. A relation between the timing of the bursts and the vector potential of the laser light is derived analytically based on a perturbative solution of a two-state model.
• F03: "Wavelength Scaling in High Harmonic Tomographic Imaging"
  Jonathan A. Wheeler,Gilles Doumy,Terry Miller,Pierre Agostini,Louis F. DiMauro Increasing the wavelength of the fundamental driving laser at constant intensity in high harmonic generation allows one to significantly increase the upper bound of the harmonic energies produced. This feature of harmonic generation is employed in an effort to improve the spatial resolution achieved in the method of tomographic reconstruction of molecular orbitals from high harmonics. Current experimental measurements and comparison with theoretical work will be presented.
• F04: "Femtosecond Dynamics and Multiphoton Ionization driven with an Intense High Order Harmonic Source"
  J. van Tilborg, T. K. Allison, T. W. Wright, M. P. Hertlein, Y. Liu, H. Merdji, R. W. Falcone, A. Belkacem We have constructed a high intensity high order harmonic source delivering 109 extreme ultraviolet photons/shot on a gas target and used it to observe multiphoton ionization and conduct femtosecond EUV-pump IR-probe experiments. Following excitation by 20-25 eV photons, we observed that the excited ethylene cation (H2C-CH2)+ experienced isomerization to the ethylidene configuration (HC-CH3)+ in 5025 fs, followed by an H2 stretch motion. Experimental data and analysis from several other performed and planned experiments will be presented as well.
• F05: "High Harmonic Generation from Multiple Orbitals in N2"
  Brian K. McFarland, Joseph P. Farrell, Philip H. Bucksbaum, and Markus Gühr Contribution from the HOMO and HOMO-1 orbitals are observed in high harmonics from N2. We discuss the harmonic modulations in the rotational revival structure due to the HOMO and HOMO-1.
• F06: "High accuracy, real time, single-shot measurement of absolute carrier-envelope phase and pulse duration for few-cycle laser pulses"
  A. Max Sayler, T. Rathje, J.V. Hernandez, W. Müller, B.D. Esry, and G.G. Paulus We develop a novel approach which allows for the simultaneous a priori single-shot measurement of carrier-envelope phase (CEP) and pulse duration for each and every few-cycle laser pulse in a kHz pulse train, virtually instantaneously. This technique builds upon the previous work of Wittmann et al. [1], which outlines a technique for determining CEP using a stereographic ionization measurement [2]. However, our approach allows for real-time assessment of these parameters, thereby permitting the signal to be used as a laser-feedback control mechanism or as an auxiliary measurement providing shot-by-shot pulse characterization for other measurements.
• F07: "Analytic Formulas for High-Order Harmonic Generation"
  M.V. Frolov, N.L. Manakov, T.S. Sarantseva, Anthony F. Starace We present closed-form analytic formulas for high-order harmonic generation (HHG) rates for both negative ions and neutral atoms. These formulas provide a fully quantum justification for the famous classical three-step scenario (TSS) of HHG as well as a correction to the well-known classical law for the HHG plateau cutoff energy.
• F08: "Zero Photon Dissociation of H2+ in Few Cycle Pulses"
  B. Gaire, J. McKenna, A. M. Sayler, M. Zohrabi, Nora G. Johnson, F. Anis, J.J. Hua, K.D. Carnes, B.D. Esry, and I. Ben-Itzhak Evidence for dissociation caused by an intense laser field with the net absorption of zero photons is conflicting. We have measured very low kinetic energy release upon H2+ dissociation in few cycle pulses -- a signature of zero photon dissociation. Comparison with solutions of the time dependent Schro127 odinger equation supports this assertion.
• F09: "Theoretical study of Carrier-envelope phase effects from three-dimensional momentum distribution of H2+ dissociation by ultrashort laser pulses"
  Fatima Anis, B. D. Esry The carrier-envelope phase (CEP) of few-cycle laser pulses can be used to control the strong-field dynamics of atoms and molecules. To study CEP effects in H2+, we have solved the time-dependent Scho127 odinger equation including nuclear vibration and rotation as well as electronic excitation, only ionization is excluded. Including nuclear rotation is essential to obtaining results directly comparable with experiment such as the momentum distribution. We show that the momentum distribution is quite sensitive to the CEP.
• F10: "Two-source double-slit interference in angle-resolved high-energy above-threshold ionization spectra of diatoms"
  M. Okunishi, R. Itaya, K. Shimada, G. Prumper, K. Ueda, M. Busuladzic, A. Gazibegovi Busuladzic, D. B. Milosevic, W. Becker Experimental data are reported and compared with molecular strong-field-approximation calculations that display an interference where four electronic quantum orbits conspire. For random orientation of the molecule, footprints of the destructive interference survive for O2, but not for N2.
• F11: "Ultrafast Science and Development at the Astra-Artemis Facility"
  Turcu, Springate, Froud, Collier, Marangos, Tisch, La Porte, Siegel, El-Taha, Kajumba, Brugnera, Procino, Newell, Williams, Greenwood, Calvert, Bryan, Cavalleri, Dhesi, Underwood, Mercer, Gabrielsen, Cogdell, Poletto, Villoresi, Frassetto, Bonora, Roper Astra-Artemis is a unique, new, ultrafast science facility under development in the UK. The paper will report on the: (a) ultrafast science experimental results obtained with Artemis on: HHG mapping of electronic structure; ultrafast molecular process; HHG with 2-colour laser fields, energy transfer in photosynthesis and (b) Artemis facility development of new ultrafast XUV and laser beamlines and time-resolved science end-stations.
• F12: "Inner and Outer Ionization of Atomic Clusters by an Intense Attosecond Laser Pulse"
  A.V. Gets and V.P. Krainov The dynamics of inner and outer ionization of atomic clusters irradiated by intense attosecond laser pulses has been considered. A comparison with the case of femtosecond pulses has been made.
• F13: "Long-term CEP stabilization of a high-power femtosecond laser by the direct locking method"
  Jae-hwan Lee, Yong Soo Lee, Juyun Park, Tae Jun Yu, Chang Hee Nam The carrier-envelope phase (CEP) of a grating-based high-power femtosecond laser was stabilized using the direct locking method. The CEP stabilization of a femtosecond oscillator was successfully maintained for a whole day. Also CEP of amplified pulses was stabilized for several hours with phase jitter of 180 mrad by adjusting the grating separation of a pulse compressor.
• F14: "Attosecond control of electron dynamics in enhanced nanolocalized fields"
  S. Zherebtsov, I. Znakovskaya, I. Ahmad, A. Wirth, O. Herrwerth, S. Trushin, V. Pervak, S. Karsch, M. Stockman, F. Krausz, M.F. Kling, J. Plenge, E. Antonsson, B. Langer, C. Graf, E. Rühl, M.J.J. Vrakking, Th. Fennel We investigated the waveform control of the electron emission from isolated SiO2 nanoparticles in intense few-cycle laser fields and compare the results to experiments in Xe for the same laser parameters. The cut-off for the emission of electrons from the nanoparticles is found to be significantly higher as compared to Xe. Model calculations indicate that the high-energy electrons arise from electron recollision in a locally enhanced field near the particle surface.
• F15: "10 kHz Accuracy Spectroscopy in Acetylene-filled Hollow-core Kagome Fiber as Measured with Optical Frequency Combs"
  Kevin Knabe, Andrew Jones, Jinkang Lim, Rajesh Thapa, Karl A. Tillman, Shun Wu, François Couny, Phillip S. Light, Natalie Wheeler, Fetah Benabid, Jeffrey W. Nicholson, Brian R. Washburn, and Kristan L. Corwin Two frequency combs are used to characterize the accuracy and stability of an optical reference based on a 12C2H2…filled, kagome-structured hollow-core photonic crystal fiber. The accuracy of this reference is ±9 kHz, and the fractional instability is 1.2 × 10-11 or less in 1 s.
• F16 O01: "Controlling the Carrier-Envelope Phase of Single-Cycle Waveforms Synthesized from Raman Generated Frequency Combs"
  Zhi-Ming Hsieh, Chien-Jen Lai, Han-Sung Chan, Sih-Ying Wu, Chao-Kuei Lee, Wei-Jan Chen, Ci-Ling Pan, Fu-Goul Yee, A. H. Kung We proposed and experimentally verified that the carrier-envelope phase of single-cycle waveforms synthesized from Raman generated frequency combs can be precisely set and controlled by generating the comb using an infrared laser tuned near a Raman resonance and the second harmonic of the laser to drive the Raman coherence.
• F17: "Generation of 3.7-fs, 1.2-mJ pulses using a hollow-fiber pulse compressor"
  Juyun Park, Jae-hwan Lee, Luu Tran Trung, Chang Hee Nam A differentially pumped neon-filled hollow-fiber pulse compressor was investigated to generate high-power few-cycle laser pulses. The pulse compression was optimized by adjusting neon pressure and laser chirp to produce the shortest laser pulses. Precise dispersion control enabled the generation of laser pulses with duration of 3.7 fs and energy of 1.2 mJ. This corresponds to an output of 1.5-cycle, 0.3-TW pulses at a 1-kHz repetition rate.
• F18 O04: "Generation of high-order harmonics with ultra-short pulses from filamentation"
  E. Schulz, D. S. Steingrube, T. Vockerodt, U. Morgner, and M. Kovacev We obtain 7-fs-pulses with 0.3 mJ after filamentation and pulse compression by double-chirped-mirrors (DCM). We use these pulses to generate high-order harmonics in a semi-infinite gas cell setup. Spectral broadening of the harmonics in different gases is observed. Especially in neon an extended continuous cut-off region down to 10 nm (124 eV) can be realized. This opens up the way to attosecond-pulse generation from filamented pulses.
• F19: "Reflective and Diffractive Optics for Coherent Ultrafast Radiation at Extreme Ultraviolet and Soft X-Ray Wavelengths"
  Yanwei Liu, Andrew L. Aquila, Farhad Salmassi, Anne Sakdinawat, Eric Gullikson We present recent developments of novel reflective and diffractive optics at the Center for X-Ray Optics (CXRO), Lawrence Berkeley National Lab, for use with coherent ultrafast x-ray sources such as high order harmonic generation and free electron lasers. At extreme ultraviolet (EUV) wavelengths, we demonstrated high efficiency multilayer-based reflective optics and the capability to fabricate aperiodic structure with optimized thickness variations for desired bandwidth and phase response, enabling pulse shaping at sub-femtosecond scale. Also described is an attosecond beam splitter, which converts a single attosecond incoming pulse into two replicas with precisely controlled time delay. This can be used in SPIDER experiments for full characterization of attosecond pulses. For coherent soft x-rays, novel diffractive optics designs implementing Fourier optics technique enables phase manipulation and provides phase contrast enhancement and extended depth-of-focus
• F20: "The Robustness of Attosecond Streaking Measurements"
  Justin Gagnon, Vladislav S. Yakovlev We investigate the robustness of one of the key tools of attosecond metrology: the attosecond streak camera. We consider the case of single and double attosecond pulses. For several key parameters of the electron wave packet, we systematically investigate how each one's uncertainty affects the spectrogram and the accuracy of the attosecond FROG retrieval.
• F21: "Strong-Field Modulated Diffraction Effects in the Correlated Electron-Nuclear Motion in Dissociating H+"
  Feng He, Andreas Beckery, Uwe Thumm By solving the time dependent SchrÄodinger equation (TDSE) for H+ 2 in a pump-probe numerical experiment, we found that the electronic motion can follow or oppose the laser electric force. Results show that the internal electron dynamics is determined by the external laser ¯eld and intra-molecular electron di®raction.
• F22: "Retrieval of target photorecombination cross sections from high-order harmonics generated in a macroscopic medium"
  Cheng Jin, Anh-Thu Le, C. D. Lin We investigate high-order harmonic generation (HHG) in a thin macroscopic medium by solving Maxwell's equation using microscopic single-atom induced dipole moment calculated from the recently developed quantitative rescattering (QRS) theory. We show that macroscopic HHG yields calculated from QRS compared well with those obtained from solving the single-atom time-dependent SchrÄodinger equation but with great sav- ing of computer time. We also show that macroscopic HHG can be expressed as a product of a macroscopic wave packet and the photorecombination cross section of the target gas. The latter enables us to extract target structure from the experimentally measured HHG spectra, thus paves the way to use few-cycle infrared lasers for time-resolved chemical imaging of transient molecules with few-femtosecond temporal resolution.
• F23: "Accurate Retrieval of Structural Information of Atoms and Molecules from Laser-Induced Photoelectron and High-Order Harmonic Spectra by Intense Laser Pulses"
  Toru Morishita, Toshihito Umegaki, Shinichi Watanabe, Oleg.I. Tolstikhin, Anh-Thu Le, Zhangjin Chen, C.-D. Lin By analyzing accurate theoretical results as well as experimental results, we established the general conclusion that laser-generated high-energy electron momentum spectra and high-order harmonic spectra can be used to extract accurate differential elastic scattering and photo-recombination cross sections of the target ion with free electrons, respectively. Since both electron scattering and photoionization are the conventional means for interrogating the structure of atoms and molecules, this result implies that existing few-cycle infrared lasers can be implemented for ultrafast imaging of transient molecules with temporal resolution of a few femtoseconds.
• F24: "High-order harmonic generation in fullerenes"
  A. Jaron-Becker, M. F. Ciappina, and A. Becker Within the Strong Field Approximation we have found that the high harmonic spectra for icosahedral fullerenes at midinfrared wavelengths show modulations in the plateau region. These modulations are due to the coherent superposition of the contributions to the dipole moment from different atomic centers of the molecule and are present in spectra for ensembles of aligned fullerenes as well as randomly oriented ones. We further show that in the case of the larger fullerenes the radius of the fullerene can be determined from the positions of the interference minima in the high harmonic spectra using a spherical model.
• F25: "Extreme ultraviolet (XUV) pulse shaping with aligned molecules"
  Zhinan Zeng, Ruxin Li, Zhizhan Xu We theoretically propose a simple scheme to shape the xuv pulse on attosecond timescale with the aligned molecule. This may offer a new way to manipulate and control the photon emission on attosecond timescale.
• F26: "Strong field dynamics with ultrashort electron wave packet replicas"
  P. Riviere, O. Uhden, U. Saalmann and J.-M. Rost We investigate theoretically electron dynamics under a VUV attosecond pulse train which has a controlled phase delay with respect to an additional strong infrared laser field. We analyze the dynamics in terms of electron wave packet replicas created by the attosecond pulses. The absorption probability shows strong modulations as a function of the phase delay for VUV photons of energy comparable to the binding energy of the electron, while for higher photon energies the absorption probability does not depend on the delay, in line with the experimental observations for helium and argon, respectively.
• F27: "Secondary electron cascade in attosecond photoelectron spectroscopy from metals"
  Jan Conrad Baggesen and Lars Bojer Madsen In a recent attosecond photoelectron spectroscopy experiment from a metal surface [A. L. Cavalieri et al. Nature (London) 449, 1029 (2007)] a tail of unexplained low-energy electrons was measured. These electrons are shown to be due to electron-electron scatterings as the photoelectrons leave the metal. We develop a model for single scattering and a model based on cascade theory to describe these electrons. Our model explains the observed background, and the amplitude of the measured streaking spectrum.
• F28: "Monte Carlo wave packet theory of dissociative double ionization"
  Henriette Astrup Leth, Lars Bojer Madsen and Klaus Mlmer Nuclear dynamics in strong-field double ionization processes are predicted using a stochastic Monte Carlo wave packet technique. The model takes input from electronic structure calculations and strong-field electron dynamics, and allows for field-dressed dynamics within a given molecule as well as several jumps between different charge states. The method is computationally efficient, applicable to a wide range of systems and relies on no empirical parameters. Nuclear kinetic energy release spectra for H2 (D2) in strong near-infrared laser pulses of 40 fs duration are compared to experiments and excellent agreement is obtained, showing the importance of accounting consistently for both neutrals and ions during the pulse.
• F29: "Analytic Theory of Few-Cycle XUV Attosecond Pulse Photoionization of Atoms"
  E.A. Pronin, M.V. Frolov, N.L. Manakov, Anthony F. Starace The doubly differential probability (DDP) for ionization of an atom by a few-cycle attosecond XUV pulse is analyzed using first and second orders of time-dependent perturbation theory (PT). We factorize the carrier-envelope phase (CEP) and angular dependence of the DDP for an initial bound S-state and analyze the general properties of CEP-induced asymmetries in photoelectron angular distributions (PADs) for an XUV pulse with arbitrary polarization and shape.
• F30: "Angle-resolved high-order above-threshold ionization spectra of inert gases in the low-frequency approximation"
  D. B. Milosevic, A. Cerkic, B. Fetic, E. Hasovic, and W. Becker We compare angle-resolved high-order above-threshold ionization spectra of inert gases obtained using the improved strong-field approximation with the spectra obtained using the low-frequency approximation.
• F31: "Amplitude and phase spectroscopy of attosecond electron wave packets"
  Kyung Taec Kim, Dong Hyuk Ko, Juyun Park, Chang Hee Nam and Jongmin Lee The interference of attosecond electron wavepackets, created by high harmonic and femtosecond laser pulses, is measured. The first electron wavepacket is generated by direct ionization of He, and the second one by the two step process of resonant excitation by the attosecond high harmonic pulse and subsequent ionization by the laser pulse. The amplitude and phase retrieved from the interferogram show the ionization dynamics of He.
• F32: "Polarization Characterization of High Harmonic Generation from Transiently Aligned Molecules"
  Xibin Zhou, Robynne Lock, Henry Kapteyn, and Margaret Murnane We perform an accurate polarimetry measurement of high harmonic emission from aligned molecules. We find that harmonic emission from nitrogen molecules can be strongly elliptically polarized; even when driven by linearly polarized laser fields. We also vary the ellipticity of the driving laser used to generate the high harmonic emission. We find that the HHG intensity from aligned molecules does not optimize with linear polarization of the driving laser (as in the atomic case), but rather peaks at a small positive or negative ellipticity. The sign and degree of this ellipticity depend on the molecular orientation.
• F33: "Angular distribution of high-order harmonic generation from aligned molecules"
  Peng Liu, Zhinan Zeng, Pengfei Yu, Ruxin Li , Zhizhan Xu We experimentally investigate the high-order harmonic generation (HHG) from aligned CO2 molecules and demonstrate that the modulation inversion of harmonic yield with respect to molecular alignment can be altered dramatically by the intensity of the driving laser pulse. The laser field dependent inversion can be explained by the shift angular distribution of harmonic emission calculated with the strong field approximation (SFA) model including a ground state depletion factor. The observed angular distributions of harmonics are discussed according to the available theoretical models.
• F34: "A new test of optical tunnel ionization"
  L Arissian, C Smeenk, C Trallero, P B Corkum Optical tunnel ionization is a powerful phenomenon at the core of attosecond science. Experiments in circularly polarized light at 800 and 1400 nm avoid electron recollision and provide a means to directly observe the tunneled electrons. We compare the measured electron wavepacket in argon to the predictions of tunneling theory.
• F35: "Angular dependence of the strong-field ionization in randomly oriented hydrogen molecules"
  Maia Magrakvelidze, Feng He, Sankar De, Irina Bocharova, Dipanwita Ray,Uwe Thumm and I.V. Litvinyuk Use coincident detection of ionized electrons and deuteron fragments to investigate angular anisotropy of tunneling ionization and correlate electron energy spectra with molecular structure.
• F36 O05: "Towards Disentangling High Harmonic Generation: Multiple Active Electrons in Strong Field Ionization of Polyatomic Molecules"
  Arjan Gijsbertsen, Andrey E. Boguslavskiy, Jochen Mikosch, Michael Spanner, Niklas Gador, Marc J. J. Vrakking, Olga Smirnova, Serguei Patchkovskii, Misha Y. Ivanov, and Albert Stolow We investigate Strong Field Ionization - the first step in High Harmonic Generation - of polyatomic hydrocarbon molecules. By utilizing a novel covariance technique we show that multiple bound electrons respond simultaneously to the strong laser field. The driven sub-cycle ionization process cannot be described within a single continuum approximation.
• F37: "High-Harmonic Generation in Polyatomic Molecules"
  M. C. H. Wong, J.-P. Brichta, V. R. Bhardwaj We investigate signatures of suppressed ionization by observing high-harmonic generation in polyatomic chlorocarbon molecules CH2Cl2, CHCl3 and CCl4 using 800nm infrared light. An extension of the high-harmonic cut-off in all molecules was observed compared to atomic Xe which has a similar ionization potential. Ellipticity measurements show broader electron wave-packet spreading for highly polarizable molecules, demonstrating the influence of multi-electron dynamics in the high-harmonic generation process.
• F38: "Effects of laser pulse duration and intensity on Coulomb explosion of CO2: signatures of charge-resonance enhanced ionization"
  Igor V. Litvinyuk, Irina Bocharova, Joseph Sanderson, Jean-Paul Brichta, Jean-Claude Kieffer, François Légaré We studied laser-induced Coulomb explosion of CO2 by full triple-coincidence momentum resolved detection of resulting ion fragments. From the coincidence momentum data we can reconstruct molecular geometry immediately before explosion. We observe the dynamics of Coulomb explosion by comparing reconstructed CO2 geometries for different Ti:Sapphire laser pulse durations (at the same intensity) ranging from few cycles (7 fs) to 200 fs. We conclude that for longer pulse durations (³100 fs) Coulomb explosion proceeds through the enhanced ionization mechanism taking place at the critical O-O distance of 8 a.u., similarly to well known charge-resonance enhanced ionization (CREI) in H2.
• F39: "Dynamic field-free orientation of polar molecules by intense two-color femtosecond laser pulses"
  Sankar De, Dipanwita Ray, Irina Znakovskaya, Fatima Anis, Nora G. Johnson, Irina Bocharova, Maia Magrakvelidze, B. D. Esry, C. L. Cocke, Matthias F. Kling and Igor V. Litvinyuk We present the first experimental observation of dynamic field-free orientation of a heteronuclear molecule (CO) induced by intense two color (800 and 400 nm) femtosecond laser pulses. We have used the two color pulse as pump to orient the molecules and a more intense 800 nm pulse as probe to measure the angular distributions. In addition to dynamic alignment seen in time dependence of average cosine square theta, we observe clear orientation in average cosine theta traces, which revives with the rotational period and can be reversed by changing the relative phase of the two colors. We studied the dependence of degree of orientation on the pump pulse intensity, and compared the results with theoretical calculations.
• F40: "Controlling Asymmetric Coulomb Explosion Using 2-Color Fields"
  K. J. Betsch, D. W. Pinkham, R. R. Jones Intense, asymmetric, two-color laser elds have been used to control directional Coulomb explosion in several small molecules. A strong asymmetry in the forward/backward fragment directionality from asymmetric dissociation channels is detected as a function of the relative phase between the 800 nm and 400 nm pulses. Manipulation of the optical phase enables control over native and/or induced electron localization in the strong optical eld. The robust eect might be utilized as an eective phase-meter for few-cycle laser pulses.
• F41: "Time-resolved laser Coulomb explosion imaging of ultrafast molecular dynamics induced in N2, O2 and CO by interaction with intense laser field"
  Irina Bocharova, Sankar De, Dipanwita Ray, Maia Magrakvelidze, Uwe Thumm, Lew Cocke, Ali Alnaser, Igor V Litvinyuk We present a series of pump-probe experiments with 8 fs 800 nm laser pulses to study the evolution of a nuclear wave packet in molecular nitrogen, oxygen and carbon monoxide following an interaction with intense laser field. We also present classical and quantum simulations of a nuclear wave packet motion which account well for our experimental data.
• F42: "Molecular Frame High Harmonic Dipole Amplitude and Phase Measurements"
  Julien B. Bertrand, Hans Jakob Wörner, David M. Villeneuve, Paul B. Corkum We use field-free alignment to generate high-order harmonics in the molecular frame. We perform parallel measurements of the harmonic yield and the ionization probability as a function of molecular alignment. Assuming the degree of alignment achieved in the experiment, we deconvolve both the molecular frame angular ionization and harmonic yield from the alignment distribution. We further discuss the coherent retrieval of the high-order harmonic dipole in the molecule’s reference frame using additional two-source interferometry phase measurements.
• F43 O07: "Attosecond Transient Absorption of High Order Harmonics in Helium"
  Mirko Holler, Florian Schapper, Johan Mauritsson, Kenneth J. Schafer, Lukas Gallmann and Ursula Keller We experimentally observe IR-assisted absorption of an attosecond pulse train in a helium gas target. We find that the transmitted photon yield not only modulates on the timescale of the envelope of the IR pulse but also detect oscillations with twice the fundamental laser frequency. We consider our experiment a first step to all-optical experiments in the attosecond domain.
• F44 O02: "Ultrafast electronic dynamics in Helium nanodroplets studied by femtosecond time-resolved EUV photoelectron imaging"
  Oliver Gessner, Oleg Kornilov, Stephen R. Leone, and Daniel M. Neumark We have performed the first femtosecond EUV-pump, IR-probe experiment to study the photoionization dynamics of pure Helium nanodroplets below the atomic Helium IP in real-time. Using Velocity-Map Imaging (VMI) photoelectron spectroscopy we were able to discern processes with associated timescales ranging from tens of femtoseconds to tens of picoseconds. The results will be discussed in the light of complementary energy-domain studies and theoretical models of the droplet’s electronic and nuclear dynamics.
• F45: "Direct Determination of Spatial Electric Field Variations"
  Steve Gilbertson, Ximao Feng, Sabih Khan, Michael Chini, He Wang, Hiroki Mashiko, and Zenghu Chang Using single isolated 276 attosecond pulses of extreme ultraviolet radiation, the transverse electric field of an 8 femtosecond Bessel-Gaussian beam was directly measured for the first time. A photoelectron replica of an attosecond burst was generated to act as a probe for the electric field of the Bessel-Gaussian beam. By monitoring the momentum shift of the photoelectrons, the direction reversing field of the laser was accurately mapped.
• F46: "Carrier-envelope phase control and stabilization by an acousto-optic programmable dispersive filter"
  N. Forget, L. Canova, X. Chen , A. Jullien and R. Lopez-Martens We demonstrate arbitrary control of the carrier-envelope (CE) phase using an acoustooptic programmable dispersive filter (AOPDF) inserted in a chirped-pulse amplification (CPA) Ti:S laser. We also demonstrate, for the first time, closed-loop CEP stabilization using an AOPDF to correct for the CEP slow drifts.
• F47p: " CAMP - A New Endstation for Simultaneous Detection of Photons and Charged Particles in Free Electron Lasers Experiments "
  D. Rolles, S. W. Epp, A. Rudenko, K.-U. Kühnelz, I. Schlichting, H. Hirsemanny, H. Graafsmay, R. Hartmann, L. Strüder, J. Ullrich We have designed a multi-purpose experimental chamber especially adapted to accommodate unique large-area, single-photon counting pnCCD detectors, developed by the Max Planck Institute Semiconductor Lab- oratory, together with advanced many-particle ion and electron imaging spectrometers (reaction microscope, REMI; velocity map imaging, VMI) for simultaneous detection of scattered and °uorescent photons and charged particles in experiments at Free Electron Lasers.

Saturday

• S01: "A robust all-non-optical method for the complete characterization of single-shot few-cycle laser pulses"
  Zhangjin Chen, T. Wittmanny, C. D. Lin We analyse the "left" and "right" asymmetry of high-energy photoelectrons along the polarization axis generated by few-cycle infrared laser pulses from atomic targets. Based on the recently developed quantitative rescattering theory, we show that the carrier-envelope phase, the pulse duration and the peak intensity of each single-shot laser pulse can be accurately and e±ciently retrieved, thus providing a robust all-non-optical method for the complete characterization of single-shot few-cycle laser pulses.
• S02: "Chirp-controlled polarization gating for isolated attosecond pulse generation"
  Florian Schapper, Mirko Holler, Lukas Gallmann, Ursula Keller We generate continuous high harmonic spectra in Argon by a superposition of two time-delayed, crosspolarized 12 fs pulses with a small imbalance of group delay dispersion (GDD) between the pulses. Our technique improves overall harmonic flux compared to traditional polarization gating methods. Recorded spectra indicate that the continuum generation is insensitive to the carrier-envelope offset phase (CEP).
• S03: "Generation of continuum harmonic spectrum using multi-cycle two-color infrared laser fields"
  Eiji J. Takahashi, Pengfei Lan, and Katsumi Midorikawa By mixing two infrared laser pulses of different wavelengths, we generate the continuum harmonic spectrum around a cut-off region. Our obtained harmonic spectra clearly show the possibility of generating isolated attosecond pulses from many-cylse laser pulse of the two color laser fields, 30 fs laser pulses centered at 800 nm and 1300 nm. This scheme makes it possible to easily create a high-energy attosecond pulse with a well-established conventional femtosecond laser system.
• S04: "Control of Electron Localization Using XUV and IR pulses"
  Kamal P. Singh, W. Cao , P. Ranitovic, S. De, D. Ray, H. Mashiko, S. Chen, F. He, A. Becker, U. Thumm, I. Litvinyuk, C. L. Cocke We demonstrate an experimental control of electron localization in the deuterium molecular ion created and dissociated by the combined action of an attosecond pulse train (APT) and a multicycle IR laser pulse. A left-right asymmetric ejection of the deuterium ions, characterized by an asymmetry parameter A, exhibits oscillations with a full IR period when the time-delay between the APT and IR pulses is scanned with 300as resolution.
• S05: "High Harmonic Generation seeded by a XUV pulse train"
  F. Kelkensberg, G. Gademann, W. Siu, P. Johnsson, M.J.J. Vrakking In the process of high harmonic generation multiple interfering quantum paths are responsible for the harmonic emission. In a theoretical study from 2004 it was shown that attosecond pulse trains can be used to select a single quantum path. The first experiment to demonstrate this effect showed an enhancement of harmonics emission by seeding it with an attosecond pulse train. Here we present for the first time the delay dependence of this enhancement demonstrating quantum path control.
• S06: "Mapping attosecond electron wavepacket motion in a molecule by using two-color laser pulses"
  Hiromichi Niikura, D. M. Villeneuve, and P. B. Corkum We measure high harmonic generation spectra of D2, N2, CO2, N2O and hydrocarbons by using simultaneously 800nm and 400 nm laser pulses generated with perpendicular polarization. The intensity of high harmonic spectra is modulated as we change the relative phase of the two pulses. The phase of intensity modulation depends on the symmetry of molecular orbitals from which high harmonics are emitted. We show that this allows us to identity any molecular orbital that can contribute high harmonic generation even randomly aligned molecule. Using this approach, we also show the observation of electron wavepacket motion occurring in a few-hundred attoseconds.
• S07: "Attosecond chirp-encoded dynamics of light nuclei"
  S. Haessler, W. Boutu, S. Weber, J. Caillat, R. Taieb, A. Maquet, P. Brege, B .Carre, P. Salieres We use the attosecond emission from light molecules to probe the ultrafast nuclear dynamics occurring between the ionization and recombination steps. By measuring the phase of the XUV emission, we have direct access to the mapping of harmonic frequency to the excursion time, which represents the delay after which the evolved molecular ion is probed. The small difference in the harmonic phase between H2 and D2 calculated theoretically is consistent with our experimental results.
• S08: "Atomic wavefunctions probed through strong field light-matter interactions"
  D. Shafir, Y. Mairesse, J. Higuet, B. Fabre, E. Mével, E. Constant, D. M. Villeneuve, P. B. Corkum, N. Dudovich The spatial properties of atomic wavefunctions were probed through the strong field process of high harmonic generation. Using elliptically polarized laser fields and two color fields we were able to manipulate the 2D motion of free electrons and probe the atomic wavefunctions from different angles. The atomic orbitals in turn were used as spatial probes to investigate the dynamics of the ionization process.
• S09: "High order harmonic generation with mid-infrared driven pulses"
  Han Xu, Hui Xiong, Yuxi Fu, Jinping Yao, Bin Zeng, Wei Chu, Ya Cheng, Zhizhan Xu We report on coherent water-window radiation by high-order harmonic generation in a gas cell with midinfrared femtosecnd pulses . With optimized parmeters, photon energy upto ~420 eV could be observed.
• S10: "High Harmonic Generation using 1425 nm sub-3 cycles laser pulses"
  F. Légaré, B. E. Schmidt, A. D. Shiner, C. Trallero, H. Worner, M. Giguère, P. B. Corkum, J-C. Kieffer, D. M. Villeneuve 13.1 fs pulses with 400 μJ pulse energy at 1425 nm have been generated using spectral broadening of OPA (Optical Parametric Amplifier) signal beam in an Ar filled hollow core fiber. Chirped mirrors are used for temporal compression and the IR few-optical-cycle pulses are applied to study the extension of the high harmonic cut-off frequency with noble gas.
• S11: "Quantum phase- and population-control in a vibrational wavepacket"
  W. A. Bryan, C. R. Calvert, R. B. King, J. Nemeth, J. B. Greenwood, J. D. Alexander, E. L. Springate, C. A. Froud, I. C. E. Turcu, I. D. Williams, W. R. Newell We present experimental evidence of the manipulation of vibrational phase and population by light-induced dynamic potential surface deformation. A vibrational wavepacket is created in D$_2^+$ in a 10 fs NIR pump pulse; the evolution of the wavepacket is non-destructively modified by a control pulse. Depending on the pump-control delay, population is up- or down-shifted and the relative phase delayed or advanced with respect to the unperturbed motion. The resulting quantum control of the wavepacket is understood in terms of a novel quasi-classical model.
• S12: " Ultrafast electron dynamics at surfaces studied using femtosecond photoelectron spectroscopy techniques "
  J. Yin, L. Miaja-Avila, G. Saathoff, S. Mathias, M. Aeschlimann, M. Bauer, M. M. Murnane, H. C. Kapteyn We directly observed the core-level relaxation dynamics in a complex surface-adsorbate system by combining laser-assisted Auger decay (LAAD) with the laser-assisted photoelectric effect (LAPE). Furthermore, we show that by using longer-wavelength driven pulses, we can more-effectively probe ultrafast dynamics using LAPE. These findings show how complex electron dynamics in solid and surface systems can be observed on femtosecond-to-attosecond time-scales.
• S13: "Generation of continuum XUV radiation by CE-phase stabilized 5-fs laser pulse"
  H. Teng, C.X. Yun, H.H. Han, J.F. Zhu, X. Zhong, Z.Y. Wei Gaining insight into the nuclear motion or electronic transitions, which falls within the attosecond (10-18 second) time scale, is the driving force to pursue new faster laser source. The coherence and short duration of attosecond laser pulses make it an attractive extreme ultraviolet (XUV) source in atomic, molecular, plasma, and solid state physics. Our goal aims to deliver a source of isolated attosecond optical pulses with shorter and more powerful for interrogating a wide range of these fundamental electronic processes in matter evolving on a ultrafast, sub 100-as timescale.
• S14: "Statistical Noise in Attosecond Pulse Retrieval"
  Sabih D. Khan, Michael Chini, He Wang, Steve Gilbertson, Ximao Feng, Zenghu Chang Measurement of single isolated attosecond pulses suffers from low photoelectron counts in the streaked spectrogram, and is thus susceptible to shot noise. We show that the reconstructed spectrogram and attosecond pulse depend on the number of photoelectron counts at the peak of the spectrogram, and find that spectrograms with a peak count number of 50 or more can be reconstructed accurately.
• S15: "Generation of XUV continuum in the plateau region of high-order harmonics driven with 7fs/800nm laser pulses"
  Yinghui Zheng, Zhinan Zeng, Hui Xiong, Yan Peng, Xuan Yang, Heping Zeng, Ruxin Li, Zhizhan Xu We show that extreme ultraviolet (XUV) continuum in the plateau of high-order harmonics (HH) can be generated in an argon gas cell by 7fs/800nm phase-stabilized laser pulses. It is based on the successful selection of single quantum path of the returning electrons during the propagation process in the gas cell. It is promising to obtain intense isolated sub 100 attosecond pulses with subsequent amplitude and phase control of the supercontinuum ranging from plateau to the cutoff region of the HH spectrum.
• S16: "Practical Issues of Retrieving Isolated Attosecond Pulse from CRAB"
  He Wang, Michael Chini, Sabih D. Khan, and Zenghu Chang The effects of streaking speed, time delay jitter, laser intensity variation and collection angle of streaked electrons on the reconstruction of isolated attosecond extreme ultraviolet (XUV) pulses from the streaked spectrogram are studied.
• S17: "Accurate Retrieval of Satellite Pulses of Single Isolated Attosecond Pulses"
  Michael Chini, He Wang, Sabih D. Khan, Shouyuan Chen, Zenghu Chang When isolated attosecond pulses are reconstructed from an ideal streaked spectrogram, the relative intensity of accompanying satellite pulses can be identified from interference. However, the interference pattern can be distorted by variation of the streaking laser intensity in the focal volume or by the use of large delay steps in acquiring the spectrogram. We investigate these effects on the reconstruction of satellite pulses with full- and half-cycle separations and find that satellite pulses with full-cycle separation are largely unaffected by these issues.
• S18: "Strong-field Below Threshold Harmonics"
  Jennifer Tate, Kenneth Schafer, Mette Gaarde We study the generation of below and near threshold harmonics in atomic gases, via calculations including single atom as well as macroscopic effects. Calculations in xenon indicate that the below threshold harmonics have multiple contributions, including one with a strongly intensity dependent dipole phase analogous to the well known long trajectory in above threshold high harmonic generation. We will also show preliminary results modeling absorption of the low energy harmonics in the presence of the strong IR field.
• S19: "Carrier-Envelop Offset Frequency Linewidth Narrowing Using an Intracavity Spatial Filter"
  Karl A. Tillman, Brian R. Washburn, and Kristan L. Corwin Significant carrier envelope offset frequency linewidth narrowing is observed in a self-referenced prism-based Cr:forsterite frequency comb when a knife edge is insert into the intracavity beam. The normally broad free-running linewidths (Dfceo) of ~1 �MHz can be reduced by as much as an order of magnitude, and then further reduced after phase-locking to <100 Hz. A simple model has been used for comparison with the observed linewidths.
• S20: "Conversion efficiency and scaling for high harmonic generation: an analytical approach"
  Edilson L. Falcão-Filho, V. M. Gkortsas, Ariel Gordon and Franz X. Kärtner Closed form expressions for the high harmonic generation (HHG) conversion efficiency are given for the plateau and cutoff regions. The results are obtained considering propagation effects, the single atom response and the single active electron (SAE) approximation. Measured absorption cross sections are used, and no parameter fitting is employed. The calculated efficiencies agree well with the experimental values published in the literature.
• S21: "Generation of CE Phase Stabilized 5 fs, 0.5 mJ, Pulses from Adaptive Phase Modulator"
  He Wang, Yi Wu, Michael Chini, Hiroki Mashiko and Zenghu Chang By improving the throughput of the 4f system and by increasing the input laser pulse energy, milli-joule level two cycle pulses were produced with a liquid crystal spatial light modulator. The carrier-envelope phase of the two-cycle pulses was measured directly by using its over-one-octave output spectrum and stabilized by feedback controlling the grating separation of the stretcher in the chirped pulse amplifier. To the best of our knowledge, this is the first time that carrier-envelope phase locked few-cycle, milli-joule level pulses were generated by using phase modulator compressors. When the pulses were used in high harmonic generation, it was found that the harmonic spectra depend strongly on the high order spectral phases of the driving laser fields.
• S22 O10: "Probing Doubly Excited Helium with Isolated Attosecond Pulses"
  Steve Gilbertson, Ximao Feng, Sabih Khan, Michael Chini, He Wang, and Zenghu Chang Single attosecond pulses generated with a neon gas target were used to probe two electron excitation and autoionization in a helium gas target. By adding an intense near infrared laser beam, the population of the excited atoms in the 2s2p1P0 state was modified in a controllable manner for the first time.
• S23: "Double Ionization of Helium Atom in Combined Near-infrared and XUV Pulses"
  Shaohao Chen, Andreas Becker We investigate the double ionization process in He atom by applying an XUV attosecond pulse in the presence of an intense near-infrared femtosecond few-cycle laser pulse. To this end, we solve the time-dependent Schrodinger equation based on a three-dimensional model. We compare the double ionization signals obtained with and without the application of the attosecond pulse.
• S24: "Multi-color attosecond control of single ionization"
  J. V. Hernandez, B. D. Esry We present the results of ab initio 6-D calculations of atomic He in intense laser fields. In particular we investigate the effect of a delay between an infrared field and an attosecond pulse train on single ionization. By casting the combined electric field of the infrared and attosecond pulse train in terms of multiple colors, an analytic framework is developed to interpret the numerical results.
• S25: "Attosecond photoionization of a coherent superposition of bound and dissociative molecular states: effect of nuclear motion"
  Szczepan Chelkowski, Andre D Bandrauk, Paul B Corkum, Jorn Manz, Gennady L Yudin We study numerically the possibility for monitoring electron motion in a dissociating molecule using an attosecond XUV probe pulse which photoionizes a coherent superposition of two nuclear wave packets prepared using a femtosecond pump pulse. We present the photoelectron spectra and forward-backward asymmetries in these spectra obtained from a numerical solution of the time-dependent Schr¨odinger equation.
• S26: "Tomographic measurement of 3D ion velocity distributions from rotationally cold molecules using a kHz VMI spectrometer"
  Xiaoming Ren, Varun Makhija, Vinod Kumarappan We measure a series of 2D velocity map images of I+ fragments from laser-aligned iodobenzene and use a filtered back-projection algorithm to reconstruct the full non-cylindrical 3D ion velocity distribution. The use of tomography in VMI is not restricted to any particular symmetry of the velocity distribution.
• S27: "Controlling the Double Photoionization Dynamics of Li Atoms by Optical Pumping"
  G. Zhu, J. Steinmann, M. Schuricke, J. Albrecht, A. Dorn, I. Ben-Itzhak, T.J.M. Zouros, J. Colgan, M.S. Pindzola, J. Ullrich Double photoionization (DPI) of lithium atoms in a magneto-optical trap by 85 eV and 91 eV photons from the Hamburg Free Electron Laser (FLASH) is investigated using cold target recoil ion momentum spec- troscopy. For ejection of a 1s and the optically excited 2p electron we demonstrate that the DPI cross section significantly depends on the alignment of the 2p valence orbital. Thus, the dynamical electron-electron correlation can be manipulated giving insight into the DPI mechanisms close to threshold.
• S28: "Controlling the Vibrational and Dissociation Dynamics of the Hydrogen Molecular Ion with Intense Infrared Laser Pulses."
  T. Niederhausen, U. Thumm, and F. Martín Using intense infrared laser pulses, we provide theoretical results for controlling the bound vibrational dynamics, the dissociation process and ionization of the hydrogen molecular ions H2+ and D2+.
• S29: "Two-center interference and nuclear motion effects in molecular harmonic generation"
  Ciprian C. Chirila, Manfred Lein The momentum spread of the returning electron in molecular high-harmonic generation (HHG) influences the harmonic phase near the two-center interference minimum. We investigate this effect using the strong-field approximation. Furthermore, we study effects of nuclear motion by simulating HHG in one-dimensional vibrating H2 molecules irradiated by laser pulses with different wavelengths. The presence of two-center interference is confirmed. We show that the ratio of harmonic signals from the isotope pair H2/D2 can be satisfactorily reproduced by a simple semiclassical model. The validity of the one-electron picture in the two wavelength regimes is established.
• S30: "Highlighting the role of dipole matrix elements in strong field molecular dissociation: vibrational suppression in H2+"
  M. Zohrabi, F. Anis, J. McKenna, B. Gaire, Nora G. Johnson, K. D. Carnes, B. D. Esry and I. Ben-Itzhak H2+ in an intense laser field shows stabilization against dissociation. We show that this stabilization can trivially be caused by the dipole matrix element coupling, without the need to summon other complex strong-field mechanisms such as vibrational trapping.
• S31: "Strong-field dynamics of a one-dimensional H+2 /H2 model molecule"
  C. B. Madsen, F. Anis, J. J. Hua, B. D. Esry We investigate the dynamics of one-dimensional (1D) H+ 2 and H2 model molecules in a strong laser field. In the case of H+ 2 we produce momentum distributions to compare with state-of-the-art experiments that resolve the kinetic energy release (KER) spectra. For H2 our main objective is to study the validity of various approximations, employed in three-dimensional (3D) calculations, by comparing our full 1D model to the 1D analogs of such approximations.
• S32: "Strong-field ionization of aligned molecules"
  M. Abu-samha and L. B. Madsen A framework for studying strong-field ionization of aligned molecules is presented, and alignment-dependent ionization yields are computed for CO2 and CS2. Our calculations are in unprecedented agreement with recent experiments, and explain the breakdown of the molecular tunnelling theory and strong-field approximation.
• S33: "Ionization, dissociation, and Coulomb explosion of H2 in intense laser fields: A theoretical study based on moving-grid approach in phase space"
  Zhongyuan Zhou, Shih-I Chu A moving-grid approach based on coupled coherent states and classical trajectories is developed for the study of dynamics of polyatomic molecules in intense laser fields. In this approach, the initial state and trajectories are determined by solving the imaginary time-dependent Schrödinger equation using diffusion Monte Carlo method. The wave function is then calculated by propagating the initial state on the moving grids guided by the classical trajectories. This approach has been applied to study ionization, dissociation, and Coulomb explosion of H2 in intense laser fields as a demonstration.
• S34: "Dynamic Stark effect and the Coulomb-Volkov approximation"
  V D Rodriguez and M G Bustamante A modified Coulomb-Volkov theory is used to study the interaction of intense laser pulses with atomic Hydrogen. Photon energy greater than the ionization potential and non-perturbative conditions are considered. The dynamical Stark effect is accounted by introducing the initial state coupling to the remaining discrete and continuum atomic spectrum. Both the Stark shift and the decay of the initial state are studied. The ionization spectra, the Stark shift and the total ionization probability are compared with results obtained from numerical solution of the time dependent Schr\"odinger equation. Both results agree well.
• S35: "Multiple orbital contribution in multiphoton ionization of H2O in intense ultrafast laser fields"
  Sang-Kil Son and Shih-I Chu We present all-electron time-dependent density-functional theory (TDDFT) investigation of multiphoton ionization (MPI) of H2O in intense ultrafast linearly-polarzied laser pulses with arbitrary molecular orientation. A new time-dependnet Voronoi-cell finite difference method featuring highly adaptive molecular grids and an efficient time propagator is applied for accurate TDDFT solutions, taking into account the detailed electronic structure and responses in multiple orbital dynamics. Our results demonstrate that the inner orbital dominantly contributes to the overall orientation dependence of H2O MPI.
• S36: "The Magnus expansion for laser-matter interaction"
  Darko Dimitrovski, Morten Foerre, Michael Klaiber, Lars B. Madsen and John S. Briggs The interaction of an atom with a short, intense few-cycle pulse including nondipole effects is described by the Magnus expansion of the time-evolution operator. The time-evolution operator obtained in this approach is particularly simple involving position and momentum shifts of the laser field and the work done by the potential. The analytical Magnus expansion results agree excellently with numerical ab initio results.
• S37: "Strong field double ionization of H2 : The phase space perspective"
  F. Mauger, C. Chandre, T. Uzerc Composed of both sequential and nonsequential process, the double ionization probability of the H2 molecule in strong laser pulses takes the form of a “knee” as a function of the intensity of the pulse. We identify the organizing structures that regulate the ionization process. Using finite-time Lyapunov maps, laminar plots, and periodic orbits, we derive reduced Hamiltonian models which help us inferring the classical mechanisms of sequential and nonsequential double ionization. Phase-space structures that regulate atomic double ionization are identified allowing verifiable predictions on the characteristic features of the “knee”, a hallmark of the nonsequential process.
• S38: "Unitary model for the ionization of atoms of hydrogen by an intense laser pulse"
  V D Rodriguez and M G Bustamante A unitary model describing the electronic transitions in an atom subject to a laser pulse is proposed. The model include the initial state coupled with both the discrete and the continuum spectrum. Continuum-continuum transitions are neglected. The model lead to a single integro-differential equation for the initial state amplitude which is solved numerically. We compare our results with TDSE simulations for hydrogen atoms.
• S39: "Tomographic reconstruction of the 3D momentum distribution in velocity map imaging experiments"
  C Smeenk, L Arissian, A Staudte, D M Villeneuve, P B Corkum We apply tomography, a general method for reconstructing 3D distributions from multiple projections, to reconstruct the momentum distribution of electrons produced by photoionization. The projections are obtained by rotating the electron distribution via the polarization of the ionizing laser beam and recording a momentum spectrum at each angle with a 2D velocity map imaging spectrometer. For linearly polarized light the tomographic reconstruction agrees with the distribution obtained using an Abel inversion. Electron tomography, which can be applied to any polarization, will simplify the technology of electron imaging. Our method can be directly generalized to other charged particles.
• S40: "Strong-field electron spectra of rare gas atoms in the rescattering region: channel closing and a simulation of the experiment"
  D. B. Milosevic, W. Becker, M. Okunishi, G. Prumper, K. Shimada, and K. Ueda We report experimental photoelectron spectra of Ne, Ar, Kr, and Xe in intense laser fields. These results are simulated using the low-frequency approximation for high-order above-threshold ionization. Resonant-like structures, observed both in the experiment and simulation, are analyzed.
• S41: "Attosecond soft X-ray pulses : From XUV attosecond pulse control by aperiodic multilayer optics to localized surface plasmon field dynamics"
  Michael Hofstetter, Casey Chew, Jingquan Lin, Nils Weber, Matthias Escher, Michael Merkel, Ulf Kleineberg XUV multilayer mirrors serve as powerful reflective optics to control the spectrum and phase of attoseocnd HHG pulses which is an important requirement for measuring time-resolved photoelectron emission dynamics from solid surfaces and nanostructures. Based on a time-of-flight photoelectron emission microscope, a new experiment for spatial and temporal characterization of photoelectron dynamics and localized surface plasmon fields is presented.
• S42: "White light generation under laser driven avalanche breakdown of air"
  Updesh Verma, A. K. Sharma A theoretical model of avalanche breakdown of air by a Gaussian laser beam and white light generation is developed. An intense laser beam, below the threshold for tunnel ionization heats the seed electrons to high energy that causes avalanche ionization of the air. However, the plasma density has a maximum on axis and falls off with radial coordinates. Such a density profile causes refraction divergence of the beam. However, temporal evolution of plasma density causes self phase modulation of the laser pulse causing frequency broadening of the pulse. The hot plasma thus produced causes strong spectral emission in the visible.
• S43: "Tunable THz Generation by Short Laser Pulses"
  Anil K Malik, Hitendra K Malik A theoretical and simulation study has been done for THz generation by direct conversion of an ultra short laser pulse into terahertz radiations. In our mechanism we use two very short laser pulses (one is circularly polarized and other is linearly polarized with same frequency while different amplitude and phases) focused on a gas which tunnel ionizes the gas. The conversion is due to ionization induced excitation in presence of static magnetic field and subsequent transverse transient current because of the presence of residual momentum after passing the laser pulse. Due to this oscillatory current THz radiation is emitted. The directionality of the emitted THz radiation is observed to be controlled by the phase difference of incident fs laser pulses. This mechanism is observed to be very efficient and is able to provide THz radiation with high power level of the order of GW.
• S44: "Collinear generation of few-cycle UV and XUV laser pulses for probing and controlling ultrafast electron dynamics at solid interfaces"
  Agustin Schiffrin, Elisabeth Bothschafter, Ulrich Graf, Eleftherios Goulielmakis, Ralph Ernstorfer, Reinhard Kienberger, Ferenc Krausz Here we discuss the implementation of the simultaneous collinear production of few-cycle UV and XUV laser pulses by high-harmonic generation of a few-cycle NIR laser pulse in two subsequent noble gas targets. Combining any of the few-cycle XUV, UV and NIR pulses will allow probing and controlling ultrafast electron dynamics in metal and semiconducting interfaces.
• S45: "Photoelectron Angular Distributions at the Ionization of Atoms by Intense Sub-one-cycle Laser Pulses"
  V.S. Rastunkov, V.P. Krainov The phase sensitivity of the photoelectron angular distributions by intense sub-one-cycle linearly polarized laser pulses has been investigated within the analytic Landau–Dykhne approximation. In both cases of sine and cosine laser pulses most of the electrons are ejected along the polarization axis of the laser field. Nevertheless the electron yield and the electron kinetic energies are much larger for the cosine waveform pulse.
• S46p: " Time-Dependent B-Spline R-Matrix Approach to Double Ionization of Atoms by XUV Laser Pulses "
  Xiaoxu Guan, Oleg Zatsarinny, Clifford J Noble, Klaus Bartschat, Barry I Schneider We have developed a general ab initio the- oretical approach for short-pulse intense laser- atom interactions, which is applicable to com- plex targets beyond (quasi) two-electron systems.
• S47p: " Toward a Multi-kHz, Multi-mJ, Few Cycle, Phase Stabilized Laser System "
  Michaël Hemmer, Andreas Vaupel, Martin Richardson The progress toward the completion of a multi-kHz, multi mJ few cycle OPCPA laser system is shown. The current and expected performances of the MOPA system generating the OPA pump beam are presented. Energies up to 0.5 mJ in a Gaussian spatial beam profile and high signal to noise ratio are currently obtained. The design and performances of the stretcher/compressor assembly are also discussed. The system is expected to provide up to 2 mJ at repetition rates in the 5 to 10 kHz range with pulse durations ~8 fs.
• S48p: " Terahertz Emission of Atoms driven by Ultrashort Laser Pulses "
  Zhaoyan Zhou, Dongwen Zhang, Zengxiu Zhao, Jianmin Yuan Terahertz (THz) emissions of an isolated atom in an ultrashort ( 100 femtosecond) laser field are simulated by solving the time-dependent Schrodinger equation (TDSE). From numerical calculations, it can be concluded that continuum THz emissions occur more readily following transitions involving intermediate states above rather than those well below the ionization threshold of the system. The models are also used to describe the observed enhanced THz emissions with a superposed second order harmonic laser field or a spatially constant electric field. Strong field approximation is extended to analyze the general features of THz emissions resulting from continuum free-free transitions of an electron in strong laser fields.

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