Chair: Heide Ibrahim, INRS-EMT, Varennes, Canada
- Tomoya Okino
- Francesca Calegari
- Davide Faccialà
- Carles Serrat
#53, 8:30 – 9:00 Attosecond nonlinear Fourier transform spectroscopy of molecule with intense a-fewpulse attosecond pulse train: observation of vibrational and electron wavepackets, TOMOYA OKINO, YUSUKE FURUKAWA, YASUO NABEKAWA, SHUNGO MIYABE, A. AMANI EILANLOU, EIJI J. TAKAHASHI, KAORU YAMANOUCHI AND KATSUMI MIDORIKAWA, Attosecond electron wavepacket in a nitrogen molecule is prepared by afew- pulse attosecond pulse train and the temporal evolution is monitored by recording kinetic energy distribution of fragment ions using a-few-pulse attosecond pulse train as a probe pulse. The temporal evolution of vibrational wavepackets are recorded for identifying the electronic states involved in the formation and probe processes of electron wavepacket. Four intensity modulations from 500 as to 3.5 fs are identified and they are ascribed to the electronic motion or charge oscillation between two electronic states composing the electron wavepacket.
#54, 9:00 – 9:15 Ultrafast electron dynamics in amino acids induced by attosecond pulses, F. CALEGARI, D. AYUSO, A. TRABATTONI, S. ANUMULA, L. BELSHAW, S. DE CAMILLIS, F. FRASSETTO, L. POLETTO, A. PALACIOS, P. DECLEVA, J. GREENWOOD, F. MARTÍN, AND M. NISOLI, Attosecond technology has been proven to be a powerful tool for the observation of ultrafast electron dynamics in atoms, molecules, and solids. Here, we report on the application of isolated attosecond pulses to trigger a purely electron dynamics in a biologically-relevant molecule, the amino acid phenylalanine, which results in charge migration mainly between the amine and the carboxylic groups on a sub–4.5-fs temporal scale. The ability to initiate and observe such electronic dynamics in polyatomic molecules opens new perspectives for attosecond science, moving toward the investigation of more and more complex systems.
#55, 9:15 – 9:30 Mapping the N2 + dissociation dynamics with attosecond temporal resolution, A.TRABATTONI, M. KLINKER, J. GONZÁLEZ-VÁZQUEZ, C. LIU, G. SANSONE, R. LINGUERRI, M. HOCHLAF, J. KLEI, M. J. J. VRAKKING, F. MARTÍN, M. NISOLI, AND F. CALEGARI, The interaction of molecular nitrogen with extreme ultraviolet radiation is at the basis of many photochemical processes occurring in the Earth’s upper atmosphere. In this work, we investigate the dissociative ionization dynamics of N2 induced by isolated attosecond pulses. The momentum distribution of the produced N+ fragments was measured as a function of pump-probe delay using a velocity map imaging spectrometer. The time-dependent measurements revealed the presence of an interference pattern between two different dissociation pathways that carries the signature of the potential energy curves activated by the XUV pulse.
#56, 9:30 – 9:45 Attosecond Probing of Xenon electronic structure by two-color HHG, D. FACCIALÀ, S. PABST, B. D. BRUNER, A. G. CIRIOLO, S. DE SILVESTRI, M. DEVETTA, N.DUDOVICH, M. NEGRO, H. SOIFER, S. STAGIRA, AND C. VOZZI, The aim of this study is probing the multi-electron behavior in xenon by two-color driven high harmonic generation. We were able to study different aspects of the xenon multi-electron response by changing the relative polarization of the two colors.
#57, 9:45 – 10:00 Strong field driven coherent XUV attosecond pulse amplification, CARLES SERRAT, JOZSEF SERES, DAVID ROCA, JOSEP M. BUDESCA, ENIKOE SERES, BASTIAN AURAND, ANDREAS HOFFMANN, SHINICHI NAMBA, THOMAS KUEHL, AN CHRISTIAN SPIELMANN, We demonstrate both theoretically and with experimental measurements that weak coherent attosecond extreme ultraviolet pulses can be amplified by carefully adjusting the delay between the extreme ultraviolet pulse and an intense infrared pulse interacting with a medium. The experimental measurements using an attosecond pulse train at 110 eV in He gas driven by intense 30-fs-long laser pulses and the performed calculations clearly demonstrate that the He gas medium behaves as an amplifier of the extreme ultraviolet pulse train.
Chair: Eric Mevel, CELIA, Talence, France
- Olga Smirnova
- Hyeok Yun
- Ayelet Julie Uzan
- Antoine Camper
- Claude Marceau
#58, 10:30 – 11:00 Time-resolving Attosecond Chiral Dynamics in Molecules with High Harmonic Spectroscopy, R. CIREASA, A.E. BOGUSLAVSKIY, B. PONS, M. C. H. WONG, D. DESCAMPS, S. PETIT, H. RUF, N. THIRE, A. FERRE, J. SUAREZ, J. HIGUET, B. E. SCHMIDT, A.F. ALHARBI, F. LEGARE, V. BLANCHET, B. FABRE, S.PATCHKOVSKII, O. SMIRNOVA, Y. MAIRESSE, AND V. R. BHARDWAJ, We describe high harmonic emission from a random ensemble of chiral molecules in mid-infrared fields. We demonstrate and explain extreme chiral sensitivity of the harmonic response to weakly elliptical fields and use it to time-resolve attosecond chiral dynamics. We predict that driving HHG with tailored circularly or elliptically polarized two-color fields allows one to increase chiral dichroism by orders of magnitude. We also show how the combination of amplitude and phase HHG measurements allows one to detect enantiomeric excess and perform full reconstruction of the time-dependent chiral response.
#59, 11:00 – 11:15 Resolving high-harmonics from multiple orbitals by two-dimensional high-harmonic spectroscopy, HYEOK YUN, KYUNG-MIN LEE, JAE HEE SUNG, KYUNG TAEC KIM, HYUNG TAEK KIM, AND CHANG HEE NAM, High-harmonic radiation from a molecule carries information on electronic structure and dynamics of the molecule. The multiple molecular orbitals contributes to the process of the high harmonic generation. Resolving the contribution of each orbital is crucial for understanding molecular dynamics. We show that two-dimensional highharmonic spectroscopy can resolve high-harmonic radiation emitted from the two highest-occupied molecular orbitals, HOMO and HOMO-1, of aligned molecules. The characteristics attributed to the two orbitals are found to be separately imprinted in odd and even harmonics.
#60, 11:15 – 11:30 Single molecule interferometer via high harmonic generation, A. UZAN, H. SOIFER, O. PEDATZUR, D. AZOURY, M. KRUGER, G. ORENSTEIN, B. BRUNNER, AND NIRIT DUDOVICH, We present a new approach in HHG spectroscopy where the signal is measured in an interferometric manner. Using multicolor fields, we can accurately “shape” the spatio-temporal properties of electron trajectories within the optical cycle. Specifically, we can manipulate the angle of ionization and recollision with attosecond-Angstrom accuracy. When such control is integrated with molecular alignment, we can induce an interferometer at the single-molecule level. In this scheme the arms of the interferometer are represented by different electrons’ trajectories. We show that the interferometric approach molecular orbital, enables a direct reconstruction of the harmonics spectral phase, providing a unique insight into the structure of the molecular orbital.
#61, 11:30 – 11:45 Nitrogen tomographic study with 1.3 μm High Harmonic Generation, S. B. SCHOUN, A. CAMPER, P. AGOSTINI, J. CAILLAT, R. R. LUCCHESE, P. SALIÈRES ,AND L. F. DIMAURO, We measured the amplitude and group delay of High Harmonics generated in nitrogen with 1.3 micron laser pulses up to 70 eV for several angles between the driving field polarization and the molecular ensemble axis of symmetry. We compare our results with an angle-averaged photoionization scattering-wave dipole. We find quantitative agreement above 30 eV and qualitative agreement over the whole spectrum. Thanks to the broader spectral range and finer sampling achieved at long wavelengths, our study emphasizes features previously undetected by High Harmonic Spectroscopy and shines a new light on the tomography of molecular orbitals using this technique.
#62, 11:45 – 12:00 Photoelectron spectroscopy of molecular nitrogen using high order harmonics of 800 nm and of 400 nm femtosecond laser pulses, CLAUDE MARCEAU, T.J. HAMMOND, GRAHAM G. BROWN, PAUL B. CORKUM, AND DAVID M. VILLENEUVE, We discuss the advantages of using an ultraviolet laser as a source for high harmonic generation based photoelectron spectroscopy. With a 400 nm pump source, we can resolve vibrational lines of three different final electronic state of the N2 + ion.
Chair: Michael Spanner, NRC Ottawa, Canada
- Martin Schultze
- Marieke Jager
- Marcus Ossiander
- Tobias Witting
- Lamia Kasmi
#63, 13:30 – 14:00 Attosecond band gap dynamics, M. SCHULTZE, K. RAMASESHA, E. BOTHSCHAFTER, A. SOMMER, C.D. PEMMARAJU, S.A. SATO, D. WHITMORE, A. GANDMAN, J.S. PRELL, L. J. BORJA, D. PRENDERGAST, K. YABANA, D.M. NEUMARK, F. KRAUSZ, AND S.R. LEONE, The transfer of electronic population from valence to conduction band states in a semiconductor is the basis of modern electronics. Now attosecond spectroscopy allows to resolve this process in real-time. The excitation of electrons across the band-gap of silicon by few-cycle laser pulses is found to induce lasting modifications to the XUV absorbance spectrum in steps in synchrony with the laser electric field oscillations, indicative of light-field induced electron tunneling . All regions of the density of states across the conduction band show persistent broadening and the electronic response is readily resolved from a slower phonon induced broadening.
#64, 14:00 – 14:15 Attosecond Transient Absorption Spectroscopy of an Insulator-to-Metal Phase Transition Material: Vanadium Dioxide, MARIEKE JAGER, CHRISTIAN OTT, CHRISTOPHER KAPLAN, ROBERT MARVEL, RICHARD HAGLUND, DANIEL NEUMARK, AND STEPHEN LEONE, Changes in the vanadium 3p core level spectrum are observed with attosecond transient absorption upon excitation of carriers into the 3d conduction band of vanadium dioxide (VO 2 ) using few cycle 800 nm near infrared (NIR) pulses. By observing ultrafast photoinduced changes to the spectrum, measurements are sensitive to the rapid rearrangements in the density of states that can result from strong electron correlation and the insulator to metal phase transition (IMT). VO 2 displays a near-instantaneous spectral response over a broad range around the vanadium M-edge, followed by a fast reshaping of the spectrum. The fast and persisting rise in absorbance at the Fermi level is suggestive of transition to a metal, and the noncongruence of the fast spectral response with thermally induced changes hints at the importance of intermediate states in mediating the material’s photoinduced response.
#65, 14:15 – 14:30 Attosecond electron dynamics on surfaces and layered systems, J. RIEMENSBERGER, M. OSSIANDER, R. KIENBERGER, Attosecond stereaking experiments performed on different solids, e.g. tungsten (110) and (100), rhenium, and magnesium (0001), leading to different delays – also depending on the excitation photon energy, will be disussed. We show results from time-resolved transport of different types of electrons through defined adlayers on a bulk material on attosecond timescale.
#66, 14:30 – 14:45 Temporal broadening of attosecond photoelectron wavepackets from Au and WO3 surfaces, W.A. OKELL, T. WITTING, D. FABRIS, C.A. ARRELL, J. HENGSTER, S. IBRAHIMKUTTY, A. SEILER, M. BARTHELMESS, S. STANKOV, D. Y. LEI, Y. SONNEFRAUD, M. RAHMANI, TH. UPHUES, S. A. MAIER, J. P. MARANGOS, AND J. W. G. TISCH, We performed attosecond streaking measurements on amorphous WO3 and polycrystalline gold films. The measurements reveal the temporal structure of the near infrared electric field at the surface Furthermore FROG-CRAB analysis yields the photoelectron wavepacket temporal broadening associated with a spread of photoelectron transport times to the surface.
#67, 14:45 – 15:00 Probe Field in Photoemission Delay Measurements on a Cu(111)-Surface: Validity of Macroscopic Laws on Atomic and Attosecond Scales, L. KASMI, M. LUCCHINI, L. CASTIGLIONI, P. KLIUIEV, A. LUDWIG, M. GREIF, M. HENGSBERGER, J. OSTERWALDER, L.GALLMANN, AND U. KELLER, An infrared (IR) pulse reflected on a copper (111) surface creates a local transient grating. The phase of this field distribution, which depends on the metal properties, is imprinted in the electron phase in a two-color photoemission process. We isolate this phase from other contributions by using the RABBITT technique. A semiclassical model describing the reflected and transmitted IR field at the surface using the Fresnel equations successfully reproduces the results, therefore indicating the validity of these equations down to the atomic and attosecond level. Due to the efficient electron screening, the transmitted field contributes negligibly to the photoelectron phase.
Chair: Ursula Keller, ETH Zürich, Switzerland
- Craig Benko
- Tadas Balciunas
- Jens Limpert
- Eric Constant
- Alexander Guggenmos
#68, 15:30 – 16:00 Extreme ultraviolet frequency combs, CRAIG BENKO AND JUN YE, Extreme ultraviolet frequency combs are a versatile tool for precision spectroscopy, strong field physics, physical chemistry and condensed matter physics. Recent work demonstrated extreme ultraviolet radiation with a coherence time greater than 1 second, far exceeding any other source of extreme ultraviolet radiation. Further, the femtosecond enhancement cavity techniques employed for extreme ultraviolet frequency combs were applied to rotationally excite molecular samples to perform high-order harmonic generation in aligned molecules.
#69, 16:00 – 16:15 A compact single cycle driver for strong field applications based on a selfcompression in a Kagome fiber, T. BALCIUNAS, G. FAN, S. HAESSLER, C. FOURCADE-DUTIN, T. WITTING, A.A. VORONIN, A. M.ZHELTIKOV, F. GEROME, G.G. PAULUS, A. BALTUSKA, AND F. BENABID, We report on Kagome fiber based self-compression of 100 μJ IR pulses to single cycle duration and demonstrate HHG in an integrated scheme which allows a compact isolated attosecond XUV source implementation above 50 eV.
#70, 16:15 – 16:30 Energetic sub-2 cycle pulses at high repetition rates: towards a new source for attoscience, S. HÄDRICH, J. ROTHHARDT, R. KLAS, G. TADESSE, A. HOFFMANN, M. KREBS, A. KLENKE, Z. VÁRALLYAY, A. DROZDY, E. CORMIER, J. LIMPERT, AND A. TÜNNERMANN, Double stage nonlinear compression in gas-filled hollowcore fibers is applied to femtosecond fiber lasers leading to compression of 0.6 mJ, 250 fs pulses to 0.2 mJ, sub-2 cycle (6.1 fs at 1030 nm) pulses at 43 kHz repetition rate (8.6 W of average power). Transmitting 712 W of average power from a kilowatt cw fiber laser with excellent beam quality and stability demonstrates the outstanding scaling capability of this approach. We will propose appropriate few-cycle optics and ideas for the stabilization of the carrier envelope phase making this approach a promising route towards >100W, multi-mJ, sub-2cycle source for attoscience.
#71, 16:30 – 16:45 Optimization and control of high power high-order harmonics generated with a 50W, 100 kHz, Yb femtosecond laser system, A. CABASSE, CH. HAZERA, L. QUINTARD, E. CORMIER, S. PETIT, AND E. CONSTANT, We generate high order harmonics in the tight focusing regime with a high power, high repetition rate laser system and define optimizing conditions to maximise the XUV flux. Despite the 50 W, high power copropagating fundamental laser, the emitted XUV beam is afterward collected, filtered and imaged with a spectrometer onto a detector that allows us to characterize the useful output XUV flux. We observe at the output of the imaging spectrometer that a XUV flux higher than 0.1 μW can be obtained at focus and be useful for experiments at high repetition rate.
#72, 16:45 – 17:00 Cr/Sc multilayer mirrors for attosecond pulses at 145 eV, A. GUGGENMOS, M. JOBST, M. OSSIANDER, S. RADÜNZ, J. RIEMENSBERGER, M. SCHÄFFER, A. AKIL, C. JAKUBEIT, P. BÖHM, S. NOEVER, B. NICKEL, R. KIENBERGER, AND U. KLEINEBERG, The development of attosecond soft X-ray sources towards photon wavelengths below 10 nm is also driving the development of suited broadband multilayer optics for shaping attosecond pulses. We present our achievements in utilizing optimized ionbeam deposited Cr/Sc multilayer mirrors for the generation of single attosecond pulses at 145 eV. Isolated attosecond pulses have been measured by soft X-ray-pump/NIRprobe electron streaking experiments and characterized using FROG/CRAB. The results demonstrate that Cr/Sc mirrors can be used as efficient attosecond optics for reflecting 600 attosecond pulses at a photon energy of 145 eV, which is a prerequisite for present and future attosecond experiments.
P3-1, Enhanced multi-colour gating for the generation of high-power isolated attoseond pulses, S. HAESSLER, T. BALCIUNAS, G. FAN, L. E. CHIPPERFIELD, AND A. BALTUSKA, We theoretically study the generation of isolated attosecond pulses by high harmonic generation driven by specially shaped laser waveforms. This complements our recent experimental work on the optimization of high harmonic generation by shaped waveforms . From a systematic analysis we devise conditions that are realistically attainable with current Ytterbium-based laser technology and should lead to robust and efficient generation of isolated attosecond XUV pulses. This is backed up by pulse characterization measurements showing that our laser source safely reaches the required specifications determined in the simulations.
P3-2, Characterisation of attosecond pulses in the temporal domain using strong field ionisation, LUDOVIC QUINTARD, ERIC CONSTANT, AND FABRICE CATOIRE, We study a new approach to characterise the duration of attosecond pulses in the temporal domain by using the ionisation process as a reference. We study the evolution of doubly charged ions with respect to the delay between an ionizing IR pulse and the XUV pulse to characterise. This evolution provides a way to access to the duration of the XUV pulse directly in the temporal domain.
P3-3, Bright attosecond pulse generation under transient phase-matching in two-colour high-order harmonic generation, BERND SCHÜTTE, PAUL WEBER, KATALIN KOVÁCS, EMERIC BALOGH, BALÁZS MAJOR, VALER TOSA, SONGHEE HAN, MARC J.J. VRAKKING, KATALIN VARJÚ, ARNAUD ROUZÉE, Experimental and theoretical study of two-colour high-order harmonic generation is presented. We show efficient continuum generation by two-colour (800 and 1300 nm), femtosecond laser pulses, up to photon energies of 160 eV. Our calculations predict the generation of a single attosecond pulse isolated by hybrid optical and transient phase-matching gating.
P3-4, Control of the Spectrum and Chirp of an Attosecond Pulse Enabled by a Microchannel-Plate Filter, KUN ZHAO, ZENGHU CHANG, AND ZHIYI WEI, A microchannel plate suppresses driving laser in attosecond pulse generation and transmits photons in the extreme ultraviolet and X-ray region. This ability enables further control and manipulation of the spectrum and chirp of the generated XUV pulses with other filters and phase-mismatch in the generation gas.
P3-5, Circularly Polarized Attosecond Pulses for Attosecond Magnetism, ANDRE D BANDRAUK
P3-6, Nuclear-Motion Effects in Attosecond Transient Absorption Spectroscopy of Molecules, JENS E. BÆKHØJ, LUN YUE, AND LARS BOJER MADSEN, We investigate the characteristic effects of nuclear motion on attosecond transient absorption spectra in molecules by comparison of spectra obtained from fixed- and movingnuclei systems. In the fixed-nuclei case the spectra show striking similarities with atomic spectra reported in the literature. For the more realistic case where the nuclei are allowed to move, we find that the attosecond transient absorption spectra show new spectral features not known from atomic studies.
P3-7, Towards XUV-pump XUV-probe attosecond experiments at the Lund Laser Centre, B. MANSCHWETUS, L. RADING, F. CAMPI, H. COUDERT-ALTEIRAC, S. MACLOT, P. RUDAWSKI, C.M. HEYL, FARKAS, F. BRIZUELA, B. KIM, A. L’HUILLIER, AND P. JOHNSSON, We present first results on two-photon double ionization of neon where the use of the full high-order harmonic spectrum from generation in argon (20 eV to 45 eV) is made possible through the use of gracing incidence optics for focusing and filtering. The measured intensities open up for future studies of molecular dynamics using an XUV-pump XUV-probe approach, and we will also report on the progress of the installation of a split-and-delay unit to be used for that purpose.
P3-8, Direct Observation of Sub-Cycle Electron Dynamics in Polycrystalline Diamond, M. LUCCHINI, S.A. SATO, J. HERRMANN, A. LUDWIG, M. VOLKOV, L. KASMI, K. YABANA, Y. SHINOHARA, L. GALLMANN, AND U. KELLER We present the first investigation of attosecond electron dynamics between valence and conduction bands in polycrystalline diamond films. Extreme-ultraviolet (XUV) attosecond pulses are used to excite electrons from the valence to the conduction band in the presence of a moderately strong IR few-cycle pulse. We observe ultrafast changes in the IR-induced absorbance, which are related to the joint density of states and the IR-induced transient polarizability. Ab initio calculations performed with time-dependent density functional theory (TD-DFT) reproduce the data and confirm our interpretation.
P3-9, Time-resolved photoemission from endohedral fullerenes, S. NAGELE , G. WACHTER, M. WAIS, R. PAZOUREK, AND J. BURGDÖRFER, We theoretically investigate the photoionization of endohedral C 60 in the time domain as probed by attosecond streaking. We show that the time delays of electrons emitted from the central atom contain the signature of confinement resonances and that they are also sensitive to molecular near-fields due to enhancement and screening of the probing streaking field by the C 60 molecule.
P3-10, Multi-photon quantum beat spectroscopy in helium, R. PAZOUREK, M. REDUZZI, P.A. CARPEGGIANI, G. SANSONE, M. GAARDE, AND K. SCHAFER, We explore quantum beats in the photoelectron signal produced when an electron wave packet created by an isolated attosecond pulse is ionized by a delayed, few cycle infrared pulse. Our calculations for helium atoms show that the broad bandwidth of the few cycle pulse creates spectrally overlapping peaks that result from one-, two- or three-photon processes from more or less deeply bound states. These beat signals can in principle be interferometrically resolved with high resolution, allowing for a direct measurement of the relative phase between ionization processes of the same or different orders.
P3-11, Spectral and dynamical effects on the vibrational distribution of H2 + after molecular ionization by a single XUV-attosecond pulse. JÉRÉMY VIAU-TRUDEL, T. TUNG NGUYEN-DANG, OSMAN ATABEK, Molecular dissociative ionization pump-probe spectroscopy, using an XUV-attosecond pump and a few-cycle IR probe, allows one to investigate the formation and subsequent dynamics of the ionic vibrational wavepacket ,. In this work, we focus our attention to the ionization step and results from a sudden approximation model are compared to those obtained using a complete description of the field induced correlated multi-electron dynamics . Vibrational distributions of H2+ shows significant deviations from the Franck-Condon profile. We discuss how these deviations are related to the fast multi-electron dynamics and why the duration of the ionizing pulse may have a strong effect on the molecular-geometry-dependent phase of the wave function.
P3-12, Modulation of Attosecond Beating in Resonant Two-Photon Ionization, L. ARGENTI, Á. JIMÉNEZGALÁN, AND F. MARTÍN, We present a theoretical study of the photoelectron attosecond beating due to interference of two-photon transitions in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, both the phase and frequency of the sideband beating significantly vary with photon energy. Furthermore, the beating between two resonant paths persists even when the pump and probe pulses do not overlap, thus permitting to reconstruct nonholographically coherent metastable wave packets. We characterize these phenomena with an analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes.
P3-13, Resonance induced harmonic generation driven by high-energy optical parametric amplifier, S. MONDAL, M. A. FAREED, N. THIRÉ, Y. PERTOT, B. E. SCHMIDT, F. LÉGARÉ, AND T. OZAKI, We investigate the response of resonant-induced harmonic generation from tin plasma using tunable wavelength driving lasers from a high energy optical parametric amplifier (OPA). Even under resonant conditions, the intensity of the resonant harmonic is suppressed when the driving laser wavelength is tuned to 1.84 μm. With these results we aim to understand the interaction dynamics of continuum electrons with the autoionizing states.
P3-14, Attosecond electron dynamics resolved by hole-assisted high-harmonic generation, JING ZHAO, XIAOWEI WANG AND ZENGXIU ZHAO, We propose an IR-pump-XUV-probe scheme to investigate electron ionization dynamics, in which the laser pulse ionizes an electron from the valence orbital, creating a hole in the atom, and the attosecond pulse probes the related electron dynamics with resonant transition from inner-shell orbital to the valence hole. By analyzing the emission spectra as a function of the time delay between the two pulses, we observe strong modulations on the emission spectra, which allow us to probe both inner and outer shell electron dynamics on the equal footing.
P3-15, Quantum trajectories in below threshold harmonic generation, WEI-HAO XIONG, JI-WEI GENG, QIHUANG GONG, AND LIANG-YOU PENG, Recently, much attention has been paid on the harmonic generation below the ionization threshold. It is known that for the harmonics in this energy range, the Coulomb potential plays an important role. To investigate this phenomenon, we schematically study the harmonic emission process in this region by numerically solving the time-dependent Schrödinger equation (TDSE) of an atom in laser fields. Though several interesting mechanisms can be deduced from a large number of numerical results, a transparent insight in to the process is eluded. We thus develop a quantum trajectory Monte Carlo method to describe this process. This method can partially consider the impact of Coulomb potential and reproduce the structures of below threshold harmonics in some degree.
P3-16, Disentangle the spatiotemporal and spectral properties of different quantum trajectories in high-order harmonic generation, LIXIN HE, PENGFEI LAN, QINGBIN ZHANG, CHUNYANG ZHAI, FENG WANG, WENJING SHI, AND PEIXIANG LU, We experimentally disentangle the quantum-path contributions in high-order harmonic generation (HHG) with spatiotemporal and spectral resolutions. By adjusting the laser intensity and focusing position, the spectrum splitting, frequency shift and intensity-dependent modulation of harmonic yields are simultaneously observed for both the short and long paths. According to the frequency shift of the measured spectra, we successfully retrieve the atomic dipole phases and the temporal chirps of both the short and long quantum paths. Based on the numerical simulations, the intensity modulations caused by the quantum path interference and the transient phase matching are also well differentiated. These results give an informative mapping of spatiotemporal and spectral features of quantum paths in HHG.
P3-17, Method to retrieve the molecular orbital from high harmonic generation beyond the planewave approximation, PENGFEI LAN, YANG LI, MEIYAN QIN, XIAOSONG ZHU, PEIXIANG LU, Molecular-orbital tomography based on high-order harmonic generation has been questioned because of the use of plane-wave approximation. Here we have theoretically proposed an approach to tomographically image the valence molecular orbital utilizing a molecular continuum-wave function beyond the plane-wave approximation. We demonstrate the feasibility of this approach using the recent experimental data [S. Haessler et al. Nature Phys. 6, 200-206 (2010)] and show that the highest occupied molecular orbital of N2 can be successfully retrieved using both Coulomb waves of a Hydrogen-like atom and two-center Coulomb waves. The retrieved molecular orbital with our method agrees better with the ab inito one than the conventional plan wave approximation method.
P3-18, Highly elliptical harmonics generated in neon gas irradiated by two-color orthogonallypolarized laser fields, S. STREMOUKHOV, A. ANDREEV, B. MAHIEU, V. MALKA, B. VODUNGBO, P. SALIERES, G. LAMBERT, We present a theoretical interpretation of the recent experimental results presented in [G. Lambert et al, Nat. Comm., 6:6167, (2015)], showing that highly elliptical harmonics can be generated in two-color orthogonally polarized laser field. We use the non-perturbative theory of the high order harmonic generation, which takes into account all possible sublevels of atomic states with given angular momentum. The results of numerical calculations, which are in good agreement with the experimental data, demonstrate undoubtedly that the high ellipticity harmonics do exist in the generated spectra. The possibility of generation of randomly polarized radiation is discussed.
P3-19, Frustrated Double and Single Ionization in triatomic molecules, A. CHEN AND A. EMMANOUILIDOU, We explore the formation of highly excited neutral fragments during the break-up of strongly-driven triatomic molecules. We show how frustrated single and double ionization depend on the laser intensity.
P3-20, Application of R-Matrix with Time-dependence Theory to Double Ionisation Using a 2-electron Outer Region, JACK WRAGG, J. S. PARKER, H. W. VAN DER HART, R-Matrix with Time-dependence (RMT) theory has been extended to cover double-ionisation processes. An application to photoionisation of He is demonstrated, with an emphasis on double-ionisation cross sections.
P3-21, Ultra-High Magnetic Field (UH-MF)-Ultrafast Polarization Phase Selective (UF-PPS) Based Attosecond Electronic Events Monitoring: New Integrated Technologies at NHMF Laboratory, KRESIMIR RUPNIK, We report results of new UH-MF-UF-PPS measurements at NHMF Laboratory. Significant improvement has been achieved in detecting UFPPS electromagnetic signatures. We outline basics of the applied technology and present examples of attosecond electron dynamics reconstructions.
P3-22, Time-dependent restricted-active-space self-consistent-field theory with space-partition concept: Beyond time-dependent R-matrix theories, HARUHIDE MIYAGI, AND LARS BOJER MADSEN, As a new framework to analyze laser-induced many-electron dynamics of atoms and molecules, the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) theory with space-partition concept is formulated. Dividing the configuration space into two parts, inner and outer regions, the TD-RASSCF wave function is constructed piecewise. The theory can describe the ejection of a few photoelectrons accurately and efficiently, and hence goes beyond the capability of other methodologies based on the traditional R-matrix theory dealing with only singleionization phenomena.
P3-23, Nonadiabatic tunnel ionization of laser-dressed p orbitals in strong circularly polarized fields, INGO BARTH, MANFRED LEIN, Numerical calculations of nonadiabatic tunnel ionization of degenerate atomic p ± orbitals in strong circularly polarized laser fields show that the results agree, in general, well with theoretical results, i.e. the counter-rotating electrons tunnel more easily. However, for strong laser fields and low laser frequencies, numerical calculations show that the ionization preference can be changed. Improved theoretical formulas of ionization rates for laser-dressed p⊥ and p || orbitals predict the numerical results very well.
P3-24, Coherent control of atomic argon ionization by two-color lasers, D. G. ARBÓ, N. CAMUS, L. FECHNER, C. LEMELL, S. NAGELE, J. ULLRICH, T. PFEIFER, S. D. LÓPEZ, J. BURGDÖRFER, AND R. MOSHAMMER, Experimental results and theoretical analysis of the ionization process of argon atoms interacting with linearly polarized two-color fields (λ 1 = 800 nm, λ 2 = 400 nm) are presented.
P3-25, The Effect of Photon-Momentum in ATI Spectra and in Time-Resolved Holography with Photoelectrons, SZCZEPAN CHELKOWSKI, ANDRÉ D. BANDRAUK, AND PAUL B. CORKUM, In most theoretical calculations describing the above-threshold ionization (ATI) the dipole-approximation is used, which is equivalent to setting the very small photon-momentum to zero. Using the numerical solutions of time-dependent Schrödinger equation (TDSE) we show that the radiation pressure on photoelectrons pushes the fast photoelectrons in the direction of the laser photon momentum whereas slow photoelectrons are pushed in the opposite direction. We also investigate the effect of photon-momentum on recently proposed time-resolved (on the sub-cycle time scale) holography with photoelectrons.
P3-26, Two-Pulse Control over Double Ionization Pathways in CO2, SONIA ERATTUPUZHA, SEYEDREZA LARIMIAN, ANDRIUS BALTUŠKA, XINHUA XIE, AND MARKUS KITZLER, Using a double-pulse scheme we visualize and control molecular dynamics taking place on intermediate states populated during different sequential double ionization pathways of CO2. Exchanging the pulse-sequence can almost completely switch the pathway.
P3-27, The role of energetic electrons in air lasing, MATHEW BRITTON, LADAN ARISSIAN, CHUNMEI ZHANG, AND PAUL B. CORKUM, An intense IR beam can ionize nitrogen gas leading to lasing from nitrogen. Understanding the mechanisms responsible for the emission at 337 nm from the plasma channel created in nitrogen will allow us to optimize the process in air, which may allow for backward lasing in atmospheric conditions. We measure the variation of the 337 nm signal with laser wavelength and ellipticity to look for signatures of collisional pumping of neutral nitrogen by energetic electrons in the generated 337 nm radiation.
P3-28, Spatial Properties of High-Harmonics, GRAHAM G. BROWN AND P. B. CORKUM, The spatial properties of high-harmonics generated with fundamental beam wavelengths of 800 nm and 1800 nm are calculated using the strong-field approximation in Nitrogen molecular gas. The generated beams exhibit Gaussian profiles to high precision and exhibit significant chromatic variation in wavefront structure. The distance from the point of generation to the virtual focal positions of the harmonics increases with harmonic order in both cases. The harmonics generated with the 1800 nm beam exhibit greater total differences in wavefront structure, but smaller differences over a given bandwidth than the 800 nm case.
P3-29, Nodal Planes and Lateral Continuum Electron Momentum Distributions in the Strong-Field Ionization of Ring-Type Molecules, A.F. ALHARBI, A.E. BOGUSLAVSKIY, N. THIRÉ, G. THEKKADATH, S. PATCHKOVSKII, B.E. SCHMIDT, F. LÉGARÉ, T. BRABEC, V.R. BHARDWAJ, AND M. SPANNER, We present TSDE-based computations which predict that some ring-type molecules have the highest probability of strong-field ionization (SFI) when the electric field of the laser is oriented along nodal planes. In such cases, a very strong node in the continuum wave function is present when ionizing along the most probable directions for SFI. Experimentally, we show that these features can be probed via high harmonic generation driven by elliptically-polarized laser pulses.
P3-30, Ab-initio TD-ADC(1) electron dynamics in CO2 molecule interacting with strong IR laser pulses: HHG spectra and coherences between the final ionic states, M.RUBERTI, V.AVERBUKH, J.P.MARANGOS, AND P. DECLEVA, We have performed a fully ab-initio 3-D TDSE calculation for the electron dynamic of the CO 2 molecule interacting with high-intensity ultra-short infrared (IR) laser pulses. Specifically, we have calculated the high order harmonic generation spectra (HHG), quantitatively investigating the effects of its multi-channel nature on its dynamical minimum. We also present the first calculation of the reduced ionic density matrix (R-IDM) resulting from the ionization of CO 2 by strong IR laser fields. We show that the final coherence between the produced ionic states is strongly affected by the IR pulse duration and moderately affected by the IR peak intensity. We also show that high coherence between the final ionic channels can be obtained with a moderately high IR intensity for very short pulses. The calculation has been performed using the recently developed  molecular time-dependent version of the ab-initio algebraic diagrammatic construction (ADC) many-body Green’s function method, in the Bspline single-electron basis.
P3-31, Steering the electron in D2 dissociative ionization by a mid-infrared two-color laser field, VINCENT WANIE, HEIDE IBRAHIM, SAMUEL BEAULIEU, NICOLAS THIRÉ, BRUNO E. SCHMIDT, YUNPEI DENG, ALI S. ALNASER, IGOR V. LITVINYUK, XIAO-MIN TONG AND FRANÇOIS LÉGARÉ, We used a mid-infrared two-color (1800 nm and 900 nm) laser field to ionize D2 molecules and steer the remaining electron during the photo-induced dissociation. We observed the simultaneous control of several fragmentation pathways, which is reproduced by ab initio calculations. The results indicate that the use of a two-color laser field rather than CEP stabilized pulses can be favourable to control electron localization.
P3-32, Strong-field physics with mid-IR wavelengths, M. G. PULLEN, B. WOLTER, M. BAUDISCH, M. SCLAFANI, H. PIRES, M. HEMMER, A. SENFTLEBEN, CLAUS DIETER SCHRÖTER, JOACHIM ULLRICH, ROBERT MOSHAMMER, AND JENS BIEGERT, A current trend in strong-field physics is the use of mid-IR radiation so that much higher energy electron and photons can be generated, and conditions in the quasi-static regime can be created without causing ionization saturation. However, the use of mid-IR fields also presents some experimental challenges. We present the recipe to solve these problems by combining a high repetition rate mid-IR source with a 3D coincidence detection reaction microscope. We highlight the versatility of the apparatus by presenting experimental results from the ionization of Xe over the meV-keV energy range.
P3-33, Spectral fine-structure control in two-colour high-order harmonic generation, EMERIC BALOGH, KATALIN KOVÁCS, BALÁZS MAJOR, BERND SCHÜTTE, PAUL WEBER, VALER TOSA, SONGHEE HAN, MARC J.J. VRAKKING, ARNAUD ROUZÉE, KATALIN VARJÚ, We combine two intense (NIR and MIR) pulses, both of 50 fs duration, to generate high order harmonics in a gas target. We observe fine-structures in the generated spectra, controlled by the subcycle delay of the two pulses. We explain the spectral features by the interference of radiation produced in consecutive half-cycles, which is temporally confined to a transient phase matching window.
P3-34, Direct access to the spectral phase inside a Fano resonance through attosecond photoionization, V. GRUSON, L. BARREAU, Á. JIMÉNEZ-GALÁN, F. RISOUD, J. CAILLAT, A. MAQUET, B. CARRÉ, F. LEPETIT, J-F. HERGOTT, T. RUCHON, L. ARGENTI, R. TAÏEB, F. MARTÍN, AND P. SALIÈRES, We measure the phase of the 2s2p Fano resonance in helium with the RABBIT technique. XUV attosecond pulse trains are created by High Harmonic Generation in a rare gas from a tunable mid-IR Optical Parametric Amplifier (OPA). We perform a detailed analysis inside the sidebands of the resonant harmonic and thus determine the spectrally-resolved amplitude and phase of the 2-photon transition. By choosing the OPA wavelength so that a given harmonic hits the resonance, a full characterization of the structured electron wave packet released in the continuum can be retrieved from a single RABBIT trace.
P3-35, Wigner time delay asymmetry in CO photoionization, L. CATTANEO, J. VOS, S. HEUSER, M. LUCCHINI, C. CIRELLI, AND U. KELLER, We present our preliminary results of photoionization delay measurements on CO molecules. Due to the asymmetric Coulomb potential electrons emitted in the same direction with respect to the C+ ion will experience a different ionization delay than those emitted in the opposite direction. The difference between these two delay times provides not only a direct insight into electron dynamics of the CO molecule but also gives access to the Wigner time delay asymmetry, which is independent of the atto-chirp and the measurement-induced continuum-continuum quantum transition delays.
P3-36, Probing delays in resonant and nonresonant above-threshold ionization, LUCAS ZIPP, ADI NATAN, PHILIP BUCKSBAUM, We have measured attosecond-scale phase delays in above-threshold ionization of atoms using a weak probe field at half the frequency of the strong ionizing laser. This technique extends the attosecond delay measurements of RABBITT into the strong field above-threshold ionization (ATI) regime, enabling us to observe intensity- and energy-dependent delays in the photoelectron spectrum. Further exploration of strong-field electron dynamics using this technique has revealed large changes in the phase of electrons ionized through transient ac Stark shifted “Freeman” resonances. These phase shifts can serve as a sensitive probe of the atomic core potential exposed to an intense laser field.
P3-37, Photo-double ionization of Xe by XUV high harmonics, using a new zero dead-time camera based multi-particle detector, M GÉLÉOC, X URBAIN, D BECH, J-P VAN ROY, S J WEBER, A HUETZ, AND Y PICARD, Detailed measurements of the photo-double ionization process require to analyze energies and angles of the two emitted electrons. A new multi-particle time and position sensitive detector is described, which combines a microchannel plates (MCPs) stack with a phosphor screen, a CMOS camera and a waveform digitizer. Particle identification relies on the COrrelation between BRightness of phosphor screen spots and Amplitude of electrical signals (COBRA). The ability of the COBRA method to measure electron pairs is demonstrated.
P3-38, Dynamical origin of near- and below-threshold harmonic generation of Cs in an intense midinfrared laser field, PENG-CHENG LI, YAE-LIN SHEU, CECIL LAUGHLIN, AND SHIH-I CHU, We perform an ab initio quantum study of the near- and below-threshold harmonic generation of cesium (Cs) atoms in an intense 3600-nm mid-infrared laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, the roles of multiphoton and multiple rescattering trajectories on the nearand below- threshold harmonic generation processes are clarified. We find that the multiphoton dominated trajectories only involve the electrons scattered off the higher part of the combined atom-field potential followed by the absorption of many photons in near- and below-threshold regime. Furthermore, only the near-resonant below-threshold harmonic is exclusive to exhibit phase locked features. Our results shed light on the dynamic origin of the near- and below-threshold harmonic generation.
P3-39, Research directions in fundamental attosecond science driven by the ELI Attosecond Light Pulse Source, G. SANSONE, D. CHARALAMBIDIS, K. OSVAY, S. BROCKHAUSER, MATHIEU DUMERGUE, S. KÜHN, P. ANTICI, E. CORMIER, P. DOMBI, J. FÜLÖP, S. KAHALY, M. KALASHNIKOV, N. LOPES, R. LOPEZ-MARTENS, RÁCZ, P. RANITOVIC, P. TZALLAS, Z. VÁRALLYAY, AND K.VARJÚ, We will review the research perspectives that will be enabled by the versatile attosecond light sources with unique characteristics of the ELI Attosecond Light Pulse Source. Examples of research applications will be discussed.
P3-40, Resolving the Dynamics of Valence-Shell Electrons and Nuclei through Laser-Induced Diffraction and Holography, SAMUEL G. WALT, N. BHARGAVA RAM, AARON VON CONTA, DENITSA BAYKUSHEVA, MARCOS ATALA, AND HANS JAKOB WÖRNER, We have studied a coupled electronic-nuclear wave packet in nitric oxide using timeresolved strong-field photoelectron holography and rescattering. We show that the electronic dynamics mainly appears in the holographic structures whereas nuclear motion strongly modulates the angular distribution of the rescattered photoelectrons.
P3-41, Bright, tunable high harmonic generation by truncated beams, HUNG-WEI SUN, PEI-CHI HUANG, YIHSUAN TZENG, REN-TING HUANG, PENG YE, MING-CHANG CHEN, By simply truncating the driving fundamental, both experimentally and theoretically we for the first time demonstrated a very high flux and a wide energy tunability of harmonics from ≈ 35 to ≈70 eV.