Session 1 – INTRODUCTION TO ATTOSCIENCE

Chair: Mauro Nisoli, Politecnico di Milano, Italy

 8:30 Welcome note by the organizers

#1, 8:45 – 9:30 Tutorial: New Frontiers in Attosecond Spectroscopy, DORON AZOURY, MICHAEL KRÜGER, OREN PEDATZUR, GAL ORENSTEIN, GIL PORAT, GIDEON ALON, AYELET UZAN, BARRY D. BRUNER, AND NIRIT DUDOVICH. Attosecond science is a young field of research that has rapidly evolved over the past decade. Leading researchers in the field have opened a door into a new area of research that allows one to observe multi-electron dynamics. I will review the main challenges and goals in attosecond spectroscopy. I will then focus on a new direction that integrates the two main branches in attosecond spectroscopy – the XUV pump-probe scheme with HHG spectroscopy. This scheme increases the dimensionality in both the measurement and control of attosecond scale processes. Furthermore, it combines the accuracy, provided by HHG spectroscopy, with the control, provided by the XUV pulses.

#2, 9:30 – 9:45 All-Optical Single-Shot Measurement of Time-Dependent Fields in Short Pulses, DONGHYUK KO AND PAUL CORKUM. We propose all-optical single-shot measurement for complete temporal characterization of attosecond pulses and femtosecond laser pulses. We overlap two laser beams noncollinearly at a gas medium to generate and perturb attosecond emissions. A weak laser field induces a moving grating and affects the harmonic generation process driven by the other strong laser field. By refocusing the diffracted beams on the imaging plane, temporal structures of the time-varying optical fields are revealed on a time-frequency spectrogram. Rigorous phase retrieval algorithm recovers the phase from the spectrogram for achieving complete reconstruction of the ultrashort optical pulses.

#3, 9:45 – 10:00 Simultaneous generation of pulses at 20 eV and 90 eV for attosecond pump-probe experiments, D. FABRIS, T. WITTING, W. A. OKELL, D. J. WALKE, P. MATIA-HERNANDO, J. HENKEL, T. R. BARILLOT, M. LEIN, J. P. MARANGOS, J. W. G. TISCH. We present a novel source of synchronised ultrafast pulses at different photon energies, generated via high-harmonic generation and uniquely suited for attosecond pump – attosecond probe experiments. We have temporally characterised the pair of pulses using attosecond streaking and a FROGCRAB algorithm and obtained a temporal duration of 576±16 as at 20 eV and 257±21 as at 90 eV.

 

Session 2 – FEW PHOTON PROCESSES

Chair: Nora Berrah, University of Connecticut, USA

  • Fernando Martin
  • Judith Durá
  • Veit Stooß
  • Romain Géneaux
  • Giuseppe Sansone

#4, 10:30 – 11:00 Attosecond pump-probe schemes for the study of electron and nuclear dynamics in molecules, FERNANDO MARTÍN, The study of attosecond electron and nuclear dynamics by making use of pumpprobe schemes will be discussed from a theoretical perspective.

#5, 11:00 – 11:15 Control of multiphoton XUV ionization of argon by intense NIR fields, JUDITH DURÁ, MARTIN FLÖGEL, ARNAUD ROUZÉE, MARC J. J. VRAKKING, We present resonance-enhanced double ionization of Aratoms in intense XUV fields. A state of the art table-top source based on HHG that produces intense XUV fields is used. By monitoring the Ar 2+ yield as a function of the XUV pulse and an additional NIR pulse, we show that the formation of Ar 2+ ions proceeds via sequential two-photon XUV ionization resulting in the formation of singly charge excited Ar +* ions that are then ionized by the NIR laser pulse. We show that the population of the Ar+* excited cations can be controlled by a Stark-shift induced by the NIR pulse.

#6, 11:15 – 11:30 Observing the onset of inversion symmetry breaking of bound states in strong fewcycle laser fields, VEIT STOOß, ANDREAS KALDUN, CHRISTIAN OTT, ALEXANDER BLÄTTERMANN, THOMAS DING AND THOMAS PFEIFER, Electronic transitions and the states accessible to optical spectroscopy of atoms are governed by the symmetries of the corresponding atomic orbitals. When strong electric fields are applied to atoms, these symmetry properties change, resulting in modified selection rules and modifications in the characteristic absorption spectrum. Here, we explore the interaction of a strong few-cycle laser pulse with neutral helium and the characteristic signatures of parity symmetry breaking obtained in transient-absorption spectroscopy. We present experimental results for inversion symmetry breaking due to the DC-Stark effect caused by intense near-visible laser pulses. This approach can be used to study and control otherwise dipole-forbidden transitions with strong fields in the time domain.

#7, 11:30 – 11:45 Attosecond electron beams carrying orbital angular momentum, ROMAIN GÉNEAUX, ANTOINE CAMPER, THIERRY AUGUSTE AND THIERRY RUCHON, We measured the orbital angular momentum (OAM) of individual harmonics in a broad high harmonic (HHG) spectrum generated with an incoming IR beam carrying 1, 2 and 3 quanta of OAM. We established the conservation laws of OAM. We further used this light source to generate electron beams carrying a vortex and measured their attosecond time structure. This new secondary electronic source opens the way to new kind of spectroscopic applications, especially in solid state science.

#8, 11:45 – 12:00 Coherent control in the extreme ultraviolet spectral range using the Free Electron Laser FERMI@Elettra, P. CARPEGGIANI, G. SANSONE, M. REDUZZI, A. GRUM-GRZHIMAILO, E.V. GRYZLOVA, S.I.STRAKHOVA, K. BARTSCHAT, D. IABLONSKYI, Y. KUMAGAI, T. TAKANASHI, K. UEDA, A. FISCHER, F. STIENKEMEIER, T. MAZZA, M.MEYER, E. ALLARIA, C. CALLEGARI, R. CUCINI, G. DE NINNO, S. DI MITRI, B. DIVIACCO, E. FERRARI, P. FINETTI, D. GAUTHIER, L. GIANNESSI, N. MAHNE, G. PENCO, O. PLEKAN, L. RAIMONDI, P. REBERNIK, E. ROUSSEL, C. SVETINA, M. TROVÒ, M. ZANGRANDO, K. C. PRINCE, In this work we demonstrate for the first time the implementation of coherent control schemes in the extreme ultraviolet (XUV) spectral range. Using the combination of two XUV fields at frequency and 2, we demonstrate the control of the emission direction in the photoionization process of neon atoms. The fields were generated by the seeded FEL FERMI@Elettra, which, thanks to its unique characteristics of stability, spectral selectivity and coherence, allows for the control of the relative phase between the two components with a resolution less than 10 attoseconds.

Session 3 – STRONG-FIELD PROCESSES I

Chair: Zhiyi Wei, Institute of Physics, Beijing, China

#9, 13:30 – 14:00 Attosecond charge migration and its laser control, P. M. KRAUS, B. MIGNOLET, D. BAYKUSHEVA, A. RUPENYAN, L. HORNÝ, E. F. PENKA, O. I. TOLSTIKHIN, J. SCHNEIDER, F. JENSEN, L. B. MADSEN, A. D. BANDRAUK, F. REMACLE AND H. J. WÖRNER, We advance high-harmonic spectroscopy to resolve molecular charge migration in time and space and simultaneously demonstrate extensive control over the process. A multidimensional approach enables us to reconstruct both quantum amplitudes and phases with a resolution of 70-130 attoseconds and to separately reconstruct field-free and laser-driven charge migration. Our techniques make charge migration in molecules measurable on the attosecond time scale and open new avenues for laser control of electronic primary processes.

#10, 14:00 – 14:15 Transverse electron momentum distribution with pulses of varying ellipticity: Cross-over from tunneling to over the barrier ionization regimes, IGOR IVANOV, ANATOLI KHEIFETS, J.E. CALVERT, S. GOODALL, X. WANG, HAN XU, A.J. PALMER, D. KIELPINSKI, I.V. LITVINYUK, AND R.T.SANG, We study transverse electron momentum distribution (TEMD) in strong field atomic ionization driven by laser pulses with varying ellipticity. We show that the TEMD in the tunneling and over the barrier ionization (OBI) regimes evolves in a qualitatively different way when the ellipticity parameter ε describing polarization state of the driving laser pulse increases. In the tunneling regime, the TEMD gradually evolves from a sharp cusp to a smooth Gaussian when ε varies from 0 to 1 (from linear to circular). In the OBI regime, the cusp remains for all ellipticities. This qualitative difference is a distinctive marker of OBI.

#11, 14:15 – 14:30 Dynamic Core Polarization in Strong-Field ionization and High-order Harmonic Generation of CO molecules, BIN ZHANG, JIANMIN YUAN, AND ZENGXIU ZHAO, The orientation-dependent strongfield ionization and high-order harmonic generation of CO molecules is investigated using the fully propagated three-dimensional time-dependent Hartree-Fock theory. We identify that the dynamic core polarization plays an important role in both these two processes, which is helpful for the future development of the ionization and HHG theories of molecules beyond the single active electron approximation.

#12, 14:30 – 14:45 Dynamic exchange and polarization in strong field ionization of molecules, VINAY PRAMOD MAJETY AND ARMIN SCRINZI, A novel hybrid anti-symmetrized coupled channels approach is used to study the undelying mechanisms in strong field ionization of molecules. It allows for the first time a systematic study of the role of various multi-electron effects like the interchannel coupling, ionic core polarization and exchange in strong field ionization. We investigated several experimentally interesting systems like N2, CO and CO2 using this method and it fully explains the observed angle dependent ionization profiles. Our calculations resolve the long debated mechanism behind the angle dependent emission of CO2, which happens to be a simple single channel process that is significantly influenced by the exchange interaction between the ionizing electron and the residual ion.

#13, 14:45 – 15:00 Sub-laser-cycle control of coupled electron-nuclear dynamics at a conical intersection, MARIA RICHTER, FOUDHIL BOUAKLINE, JESÚS GONZÁLEZ-VÁZQUEZ, LARA MARTÍNEZ-FERNÁNDEZ, INÉS CORRAL, SERGUEI PATCHKOVSKII, FELIPE MORALES, MISHA IVANOV, FERNANDO MARTÍN, AND OLGA SMIRNOVA, We discuss new opportunities for controlling coupled electron-nuclear dynamics, offered by the advent of nearly singlecycle, phase-stable mid-infrared laser pulses. The key idea of the control scheme is to match the time scale of the laser field oscillations to the characteristic time scale of the wave packet transit through the conical intersection (CI) region. The instantaneous laser field changes the shape and the position of the conical intersection as the wave packet passes through. As the CI moves in the laser field, it ‘slices’ through the wave packet, sculpting it in the coordinate and momentum space.

Session 4 – ATTOSECOND LIGHTHOUSE

Chair: Ming-Chang Chen, National Tsing Hua University, Hsinchu, Taiwan

#14, 15:30 – 16:00 Attosecond sampling of arbitrary light waves, KYUNG TAEC KIM, KYUNGSEUNG KIM, CHUNMEI ZHANG, D. M. VILLENEUVE, P. B. CORKUM AND CHANG HEE NAM, An arbitrary optical waveform can be completely determined by measuring phase shifts of high harmonic radiation altered by an additional signal field. Since the electron motion in the process of high harmonic generation is used as a fast gate, the temporal resolution of the waveform measurement is related with the excursion time of the electron trajectory. Here we show that the waveform measurement exhibits strong wavelength dependence for short wavelength signals. Our calculations show that the signal field in the ultraviolet wavelength range can be accurately measured when the wavelength dependence of the measurement is taken into account.

#15, 16:15 – 16:30 Gating Attosecond Pulses in a Noncollinear Geometry, M. LOUISY, C.L. ARNOLD, M. MIRANDA, E.W. LARSEN, S. BENGTSSON, D. KROON, M. KOTUR, D. GUÉNOT, L. RADING, P. RUDAWSKI, F. BRIZUELA, F. CAMPI, B. KIM, A. JARNAC, A, HOUARD, J. MAURITSSON, P. JOHNSSON , A. L’HUILLIER , AND C.M. HEYL, We experimentally demonstrate that angular streaking of attosecond pulses in a noncollinear geometry is a suitable gating technique for high-order harmonic sources. Our results indicate the generation of angularly separated isolated attosecond pulses whose direction of emission can be controlled by the carrier envelope phase of the driving laser pulses. This technique is particularly suited for attosecond pump-probe measurement and intra-cavity attosecond pulse generation, as the noncollinear geometry naturally separates the fundamental driving field from the generated attosecond pulses and, as no major manipulations of the driving field are required.

#16, 16:30- 16:45 Full characterization of Attosecond Pulses Generated by Ultrafast Wavefront Rotation, TJ HAMMOND, CHUNMEI ZHANG, KYUNG TAEC KIM, GRAHAM G. BROWN, D.M. VILLENEUVE, AND P.B. CORKUM, The attosecond lighthouse is a method of using ultrafast wavefront rotation to create a series of spatially separated attosecond pulses. We present the results of two experiments, characterizing attosecond pulses generated by the lighthouse from 760nm and 1.8m sources. Photoelectron streaking is performed on the three most intense pulses generated by a kHz Ti:Sapphire laser. For longer driving wavelength, we use an in-situ measurement for spatial and spectral characterization, which is scalable to the soft X-ray spectral region. In both cases, the reconstructed, isolated pulses are compared to theory.

#17, 16:45 – 17:00 Ionization induced lighthouse effect in Ar, V. TOSA, J.S. LEE, H.T. KIM, C.H. NAM, High harmonic generation under high ionization conditions is numerically investigated. A new structure of the driving field during propagation is obtained and characterized in temporal, spectral and spatial domains. The complete depletion of neutral Ar on axis gives rise to additional wavelets which propagate with increasing divergence as the radial distances from the axis increases, generating the rotation of the propagated wavefront. We obtain attosecond bursts of light emitted with different divergences in successive optical half-cycles so that in the far field these bursts arrive at different distance from the beam axis.

#18, 17:00 – 17:15 High flux isolated attosecond pulses from non-collinear high-order harmonic generation, SHIYANG ZHONG, XINKUI HE, HAO TENG, KUN ZHAO, ZHIYI WEI, We proposed a new approach for producing high flux isolated attosecond pulses (IAPs) based on non-collinear geometry of high order harmonic generation (HHG). A main driving pulses and a short gating pulse is non-collinearly synthesized to form a rotated wavefront which leading to spatially separated IAP generation. Since the new approach no restriction on the pulse duration of the main driving pulse, it enables the present super-high energy laser could be used as driving laser for high flux IAP generation.

Poster Session I

#P1-1, High Harmonic Generation and Vacuum Ultraviolet Spectra Generated from Two-color Laser Fields Induced Ar Plasma, WEI-JAN CHEN, CHIEH-CHUAN CHEN, CHAN-SHAN YANG, AND CI-LING PAN, High harmonic generation is not only a major source of attosecond pulse, but also an important coherent VUV light source. These harmonics generation from laser induced Ar plasma were initiated by a Q-switched Nd:YAG laser fundamental (1064 nm) and second harmonic generation (532 nm) at the focused intensity of around 1013 W/cm2. Besides the harmonics generation, the characteristics of a continuous VUV spectrum generated from two-color laser fields induced Ar plasma are also investigated. We study the enhancement of harmonics generation and the continuous VUV spectra by the waveform control of this two-color laser fields. These results are useful for the understanding of harmonics generation and VUV spectra from laser radiation in plasmas.

#P1-2, Tailoring Few-Cycle Optical Waveforms to Enhance High-Harmonic Production by Optimizing the Photoelectron Dynamics, O.V. MESHKOV, M.YU. EMELIN, A.A. SILAEV, N.V. VVEDENSKII, M.YU. RYABIKIN, Optimal few-cycle laser waveforms are found, which ensure highly efficient optical-to-soft-x-ray frequency conversion via high-order harmonic generation in gases. High efficiency of this process in optimal conditions is explained by the peculiarities of the photoelectron dynamics.

#P1-3, Fourier Domain Configuration for Intrapulse Frequency Mixing, GUILMOT ERNOTTE, PHILIPPE LASSONDE, FRANÇOIS LÉGARÉ, BRUNO E. SCHMIDT, We demonstrate an all-inline scheme for intrapulse differencefrequency generation (DFG). Employing a 4-f setup allows independent manipulation of the phase, amplitude and polarization of the two corresponding spectral side bands. After filamentation in air, the broadened Ti:Sa spectrum is tailored in a 4-f setup to generate mid-infrared (MIR) pulses tunable around 1.8 μm and 3.2 μm, respectively, for subsequent seeding of carrier envelope phase (CEP) stable optical parametric amplifiers (OPA).

#P1-4, Subattosecond KeV Beats of High- Harmonic X-Ray Field Produced with Midinfrared Laser Pulses: Magnetic-Field Effects, A.S. EMELINA, M.YU. EMELIN, M.YU. RYABIKIN, Based on the theoretical description beyond the dipole approximation we demonstrate that the magnetic field of laser pulse does not destroy the mechanism of subattosecond keV beats production at the trailing edge of midinfrared laser pulse. However, the possibility to shorten the duration of such keV beats with increasing laser wavelength is limited due to the electron magnetic drift.

#P1-5, 2.6 mJ energy and 81 GW peak power femtosecond laser-pulse delivery and spectral broadening in inhibited coupling Kagome fiber, B. DEBORD, F. GÉRÔME, P. M. PAUL, A. HUSAKOU, J. F. HERGOTT, AND F. BENABID, We report on 800nm laser-pulse delivery record by using inhibited coupling Kagome fibers. Strong spectral broadening and projected pulse compression down to ~10fs were achieved with input 2.6mJ energy and 81GW peak power.

#P1-6, A 1 kHz, 500 μJ Mid-IR OPCPA laser system, JIE LI, YANCHUN YIN, XIAOMING REN, ANDREW CHEW AND ZENGHU CHANG, A 1 kHz OPCPA laser source with bandwidth spanning from 1.2 to 2.2 μm is being developed for generating isolated attosecond pulses in the water window. Both the seed and pump are delivered by a 1 kHz, 17 mJ Ti:Sapphire laser system and stretched to 4 ps for broadband OPCPA processes in BIBO crystals. With two-stage amplification, 500 μJ mid-IR laser pulses have been achieved and compressed by a bulk of fused silica. We anticipate to boost the energy to 10 mJ with a third amplification stage pumped by 100 mJ Ti:sapphire laser pulses.

#P1-7, Sub-cycle energy shifts and ion build-up in strong-field ionization of xenon, M. SABBAR, H. TIMMERS, D. M. NEUMARK AND S. R. LEONE, We used attosecond transient absorption to investigate strong-field ionization in xenon atoms. After tunnel ionizing the Xe target, we probe the evolution of the valence hole via a coreto-valence transition driven by a single attosecond pulse. We have found a number of hitherto unobserved absorption features which will help to elucidate the nature of tunnel ionization in atoms.

#P1-8, Dressing Wavelength Dependent Correlated Attosecond Transient Absorption in Helium Atoms Above the Ionization Threshold, XIAOXU GUAN, MENGXI WU, METTE B. GAARDE, AND KENNETH J. SCHAFER, We present a theoretical study of transient absorption processes in helium atoms in an extreme ultraviolet (XUV)-near infrared (NIR) pump-probe scheme. We employ an ab initio, full-dimensional calculation of the two-electron dynamics, and we focus on the energy domain above the first ionization threshold. By changing from the experimentally studied 730-nm case to a laser wavelength of 1000 nm we observe light-induced states made by the strong coupling of dipole allowed and dipole forbidden states.

#P1-9, Molecular interferometer using XUV attosecond pulses to unravel electron and nuclear dynamics, ALICIA PALACIOS, ALBERTO GONZALEZ-CASTRILLO, AND FERNANDO MARTIN, Two identical XUV attosecond pulses interact with the hydrogen molecule creating an interferometer resulting from the direct and sequential twophoton absorption paths reaching the same nal ionized states. The dependence of the ionization yields with the time delay between the pulses allows to reconstruct the pumped vibronic (electronic and vibrational) wave packet created in the singly excited states of the molecule. The use of XUV pulses avoids a laser-induced distortion of the molecular potential, ensuring the characterization of the intrinsic behaviour of the system.

#P1-10, Time delays in multi-photon above-threshold ionization, S. NAGELE, S. D. LOPÉZ, D. ARBÓ, AND J. BURGDÖRFER, We theoretically analyze time-resolved above-threshold ionization (ATI) as probed by an interferometric measurement technique. We investigate the time delays in the multi-photon ATI process as a function of the number of involved photons and the intensity of the ionizing UV field and identify IR-probe field induced contributions to  the time shifts.

#P1-11, Time-dependent photoelectron momentum structures with attosecond time-resolution, HIROMICHI NIIKURA AND TORU MORISHITA, We measured the time-dependent photoelectron momentum distributions of rare-gas atoms which are ionized by irradiation of both attosecond pulse trains (APT) and an intense, infrared IR pulse using a velocity map imaging technique. For neon, we observed that the characteristic orbital-like structure appears around the zero-kinetic energy range and the symmetry varies with the sub-cycle attosecond delay between APT and IR.

#P1-12, Attosecond nanoplasmonic imaging with photoemission electron microscopy, SUNG-HO CHOI, YEON LEE, SEUNGCHUL KIM AND DONG-EON KIM, In this study, we show our research activity on attosecond streaking imaging of nano plasmonic field via photoemission electron microscopy(PEEM). For that, we introduce newly developed attosecond beam line based on 300 kHz optical parametric chirped pulse laser system. IR pump-XUV probe beam is delivered to the PEEM through specially designed normal incidence mirror inside PEEM to be suitable for plasmonic streaking experiment. This technique is able to reveal the dynamics of nano plasmonic field with nanometer spatial resolution.

#P1-13, Attosecond Transient Absorption Spectroscopy of an Electronic Wavepacket in Argon, WEI CAO, ERIKA R. WARRICK, DANIEL M. NEUMARK, AND STEPHEN R. LEONE, An electronic wavepacket composed of multiple bound Rydberg states in atomic argon between 14.6 and 16 eV is created using a broadband XUV pulse. A timedelayed few-femtosecond near-infrared (NIR) pulse interrogates the initial excitation by perturbing the induced polarization, providing simultaneous observation of individual quantum beats of the wavepacket. High spectral resolution and sub-femtosecond time resolution reveal oscillations on numerous timescales, from 5 fs beating near the ionization potential to subcycle (1.3 fs) beating in lower states. Second order perturbation theory suggests the observed beating is caused by two mechanisms: the non-resonant AC Stark effect and resonant 2-photon coupling.

#P1-14, All-Optical Phase Zone Plate for High Harmonic Generation, ZHENGYAN LI, GRAHAM BROWN, PAUL CORKUM, An all-optical Fresnel phase zone plate for XUV high-harmonic generation is formed, by interfering the intense, ultrafast driving laser field with a diverging/converging weak perturbing field. Far-field measurements of the zone plate diffraction pattern reveal information about the near-field high-harmonic wavefront.

#P1-15, The interplay between resonant enhancement and quantum path dynamics in harmonic generation in helium. SETH CAMP, KENNETH J. SCHAFER, AND METTE B. GAARDE, We present a theoretical study of the influence of resonant enhancement on quantum path dynamics in the generation of harmonics above and below the ionization threshold in helium. We find that both the short and long quantum path contribution to the harmonic yield are enhanced through bound state resonances. We analyze the sub-cycle time structure of the harmonic yield in the vicinity of the resonances and find that on resonance, the long trajectory contribution is phase shifted by approximately π/4.

#P1-16, High order harmonic generation of aligned stretched N2 molecules, YINGCHUN GUO, BINGBING WANG, Frequency domain theory is employed to calculate HHG spectra of N2 with different nuclear distances under linearly polarized laser fields. This study is of interest to investigate the dissociation process of a molecule by probing HHG spectra. We find that the cutoff frequency of HHG remains unchanged while the relative intensity of each harmonics changes with R increasing, Especially, when the nuclear distance increases, the intensities of lower order harmonics near the beginning of the spectrum decrease, while the intensities of higher order harmonics near the cutoff of the spectrum increase. These phenomena are due to the change of relative weight of s and p atomic orbitals in the molecular wavefunctions with R increasing.

#P1-17, Electron-Ion Coincidence Detection of Two-Photon Double Ionization Driven by Intense Attosecond Pulse Trains, THUSHANI N. HERATH, ALEXANDER H. WINNEY, YUN FEI LIN, PRADIP ADIKAHRI, CUN SHUN HUANG, SUK KYOUNG LEE, AND WEN LI, Ion-electron coincidence measurements are reported for the first time in two-photon double ionization of xenon driven by an intense high harmonic generation (HHG) source. Sequential double ionization is seen to be the dominant pathway in the observed energy spectrum in coincidence with xenon dication.

#P1-18, Enhancing high harmonic flux, M. SAYRAC, A. A. KOLOMENSKII, S. ANUMULA, Y. BORAN, G. KAYA,N. KAYA, AND H. A. SCHUESSLER, High harmonic generation (HHG) is a technique to generate coherent radiation in the XUV region and enabling attosecond pulse generation. However the photon flux of generated harmonics is low. In this paper, we describe the optimization of XUV radiation by three different approaches namely using a gas mixture (H2-Ne), by pressure optimization (with Ar gas), and enhancing the HH yield via molecular alignment (with N2 molecule).

#P1-19, Circularly polarized harmonic from p-type orbitals using bi-chromatic counter rotating circularly polarized laser fields, LUKAS MEDIŠAUSKAS, JACK WRAGG, HUGO VAN DER HAART, MISHA YU. IVANOV, Spectra of circularly polarized harmonics is calculated by numerically solving the Time-Dependent Schrödinger Equation for a 2D model of Ne atom using circularly polarized fundamental with counter-rotating second harmonic laser fields. A strong asymmetry is found between left- and right- circularly polarized harmonics when a ground state with p-type symmetry is used. A resulting train of circularly polarized attosecond pulses is demonstrated.

#P1-20, Ultrafast EUV Absorption Spectroscopy for Non-equilibrium Warm and Dense State of Matters, JONG-WON LEE, XIAOTAO GENG, CHANG-LYOUL LEE, DONG EON KIM, BYOUNG-ICK CHO, An experimental apparatus for ultrafast EUV spectroscopy for ultrathin foil sample irradiated by an intense laser pulse is presented. Large laser pulse energy, EUV imaging, large area sample and a fast translation system are integrated to investigate EUV absorption of warm dense nickel sample with a few eV electron temperatures with a limited number of laser shots.

#P1-21, Harmonic generation with ultrafast circularly polarized pulses on Benzene, MICHAEL JENSEN, EMMANUEL PENKA, ANDRE D. BANDRAUK, We present numerical simulations using real time Density Functional Theory [1] of the variations of orbital population and the harmonics generated when 800 nm circularly polarized ultrafast laser pulses are shone on single and dimers of Benzene. Molecules are a preferred media over atoms for circular harmonics due to their non-spherical symmetry. Varying intensities are considered, and varying numbers of optical cycles. These results are compared with similar results obtained with linearly polarized light of the same wavelength and intensity and are interpreted in terms of laser induced re-collision [2]. The polarization of the harmonics is also studied according to [2].

#P1-22, Tunneling time in strong field ionisation, A.S. LANDSMAN, T. ZIMMERMANN, AND S. MISHRA, Tunneling time definitions are calculated in the adiabatic limit of strong field tunnel ionization by the exact solution of the Schrodinger equation in a static electric field. We find that all definitions give finite tunneling times. In addition, the short-range potential approximation agrees well with the exact solution as long as one stays sufficiently far from over-the-barrier ionization regime.

#P1-23, Multiphoton and tunneling ionization probability of atoms and molecules in an intense laser field, SONG-FENG ZHAO, LU LIU, AND XIAO-XIN ZHOU, We theoretically studied ionization of atoms exposed to an intense laser field by using three different methods, i.e., the numerical solution of the single-active-electron approximation based time-dependent Schrödinger equation (SAE-TDSE), the Perelomov-Popov-Terent’ev (PPT) model, and the Ammosov-Delone-Krainov (ADK) model. The ionization of several linear molecules in a strong laser field are also investigated with the molecular ADK (MO-ADK) and the molecular PPT (MO-PPT) models. We show that the ionization probability from the PPT and the MO-PPT models agrees well with the corresponding SAE-TDSE result both in the multiphoton and tunneling ionization regimes.

#P1-24, Time-dependent R-matrix theory for atoms in mid-IR laser fields, O. HASSOUNEH, A.C. BROWN AND H.W. VAN DER HART, Time-dependent R-matrix theory has been applied to study atomic dynamics in laser fields with wavelength up to 1800 nm. We demonstrate the accuracy of the associated computer codes through the investigation of high-harmonic generation in Kr and Xe and through the extraction of ejected-electron distributions from the final wavefunction for F-.

#P1-25, Revealing correlated electronic and nuclear dynamics in molecule with energy-resolved population imaging, QINGBIN ZHANG, KUNLONG LIU, XIAOSONG ZHU, PENGFEI LAN AND PEIXIANG LU, We explore a method, named energy-resolved population imaging (EPI), to analyze on an equal footing the temporary electronic transition and nuclear motion during laser-molecular interaction, transparently demonstrating the population transfer in the H2+ exposed to the extreme ultraviolet pulses.

#P1-26, Spectra asymmetrically broadening in above-threshold ionization with XUV pulse train and intense IR laser fields, LIFENG WANG, MIN LIU, HAO TENG, BINGBING WANG, LIANGYOU PENG, XINKUI HE, SHIYANG ZHONG, PENG YE, PENG HE, MINJIE ZHAN AND ZHIYI WEI, The atomic ionization of electron is investigated in the presence of an XUV pulse train and an IR laser field with intensity of 5.7×1013 W/cm2. Compared with the spectrum generated only by the XUV pulse train, the above-threshold ionization spectrum in the two-color field is asymmetrically broadened. Simulation results based on the frequency-domain theory qualitatively agree with the experimental spectra. The experimental observations can be explained by a clear two-step ionization picture: an electron wavepacket is ionized from the ground state by the XUV field, and its energy is asymmetrically changed by absorbing or emitting specific IR photons.

#P1-27, Attosecond transient absorption spectroscopy with R-matrix theory, ANDREW C. BROWN, HUGO W. VAN DER HART, We present results from the application of R-matrix with time-dependence theory to attosecond transient absorption spectroscopy. The theory and its associated computer code is uniquely placed to model this process which is prohibitively sensitive to detailed atomic structure effects which are captured well by R-matrix theory.

#P1-28, Laser pulse duration can control the breakage of multiple chemical bonds, X. XIE, E. LÖTSTEDT, S. ROITHER, S. ERATTUPUZHA, S. LARIMIAN, D. KARTASHOV, M. SCHÖFFLER, K. MIDORIKAWA, A. BALTUŠKA, K. YAMANOUCHI, M. KITZLER, We show that the interplay of electron removal and nuclear dynamics on the few femtosecond range, controlled by the duration of few-cycle laser pulses, determines the ratio of C2H4 3+ fragmentation into two respectively three moieties.

#P1-29, Time-delays in sequential double ionisation due to correlation-induced tunnelling, J. KAUSHAL AND O. SMIRNOVA, We present a quantum-mechanical theory on time delays induced by long-range and correlation effects in strong field, nonadiabatic tunnelling ionisation of noble gas atoms, including a detailed study on the delays induced in the dynamics of the hole wavepacket left behind after the first ionisation.

#P1-30, Attosecond beam-line equipped with Angle Resolved Time of Flight (ARTOF), YEON LEE, GENG XIAOTAO, SEUNGCHUL KIM, PAENGRO LEE, JINWOOK CHUNG AND DONG EON KIM, We report the construction of an attosecond beam-line equipped with ARTOF measurement. A high rep. rate, high power, CEP-stabilized laser at 300 kHz is the main driver for attosecond XUV pulse and femtosecond XUV and UV pulses. Acceptance angle 44 degree and resolution up to 0.1 meV ARTOF is integrated. This beam-line is aimed to study the ultrafast change of band structure in 2D k-space and electron-electron correlation in condensed matter systems.

#P1-31, Intense above-300 eV XUV pulses generated by HCF-compressed few-cycle mid-IR pulses in a high-pressure gas target, CHRISTIAN STRÜBER, ALLAN S. JOHNSON, DAVID WOOD, PALOMA MATÍA-HERNANDO, TOBIAS WITTING, DANE R. AUSTIN, JOHN W. G. TISCH, JON P. MARANGOS, We demonstrate the generation of intense XUV pulses with photon energies in the water window by High Harmonic Generation (HHG) of few-cycle mid-IR pulses in a dense gas target. We use the spatial and spectral reshaping of 1.7 μm mid-IR pulses in a gradient pressure hollow core fibre (HCF) to compress the pulses to 9.1 fs, corresponding to 1.6 optical cycles, and improve its transverse profile. To obtain gas pressures in the HHG target of above 1 bar a custom-made differential pumping setup is employed.

#P1-32, Sub-cycle interference and recollision dynamics of photoelectron holography in the nonadiabatic tunneling regime, XIANHUAN YU, ZHIHAO SHENG, XIAOHONG SONG, PENG LIU, WEIFENG YANG, AND JING CHEN.

#P1-33, Carbon K-edge NEXFAS spectroscopy with a soft x-ray high harmonics source, S. L. COUSIN, F. SILVA, S. TEICHMANN, M. HEMMER, B. BUADES, AND J. BIEGERT, A high-flux table-top coherent soft x-ray high harmonic generation source, driven by sub-2-cycle, 1.85 μm, 1 kHz laser pulses, is applied to a condensed phase sample revealing the carbon binding orbitals of polyimide.

#P1-34, Towards multidimensional spectroscopy with ultrashort XUV and soft x-ray pulses, THOMAS DING, ALEXANDER BLÄTTERMANN, CHRISTIAN OTT, ANDREAS KALDUN, VEIT STOOSS, MARC REBHOLZ, PAUL BIRK, KRISTINA MEYER, AND THOMAS PFEIFER, We present first experimental steps towards XUV/soft x-ray multidimensional spectroscopy. Firstly, we demonstrate the optical control of dipole-allowed and dipole-forbidden 2s-hole states in neon using a sequence of three ultrashort pulses (XUV-VIS-VIS). Secondly, we present the design of a novel multidimensional XUV/soft x-ray spectroscopy setup, which currently is in the built-up and test phase.

#P1-35, Quantum path analysis for optical waveform measurements, KYUNGSEUNG KIM, CHANG HEE NAM, KYUNG TAEC KIM, Electron trajectories in the process of high harmonic generation provide sub-cycle temporal resolution for the optical wave-form measurement. Quantum paths of electrons in the strong laser field are analyzed using the saddle point model and the time-de-pendent Schrödinger equation. We show that the frequency response of the waveform measurement should be taken into account for the accurate waveform measurement.

#P1-36, Tunable single-order harmonic beam created by a multilayer mirror monochromator, EIJI J. TAKAHASHI, MASATOSHI HATAYAMA, SATOSHI ICHIMARU, AND KATSUMI MIDORIKAWA, We propose and demonstrate a method to monochromatize multiple orders of high harmonics by using a proper designed multilayer mirror. Multilayer mirrors designed by our concept realize the perfect extraction of a single-order harmonic from multipleorder harmonic beam, and exhibit broadband tunability and high reflectivity in the soft-x-ray region. This device is very useful for ultrafast soft x-ray experiments that require high-order harmonic beams, such as femtosecond/attosecond, time-resolved, pump-probe spectroscopy.

#P1-37, Transient Impulsive Electronic Raman Redistribution, S. MIYABE, K. MIDORIKAWA, P. H. BUCKSBAUM, Resonant Raman excitation by ultrafast vacuum ultraviolet laser pulses is a powerful means to study electron dynamics in molecules, but experiments must contend with linear background ionization: frequencies high enough to reach resonant core-valence transitions will usually ionize all occupied orbitals as well, and the ionization cross sections are usually dominant. Here we show that attosecond pulses can induce a process, transient impulsive stimulated Raman scattering, which can overwhelm valence ionization. Calculations are performed for atomic sodium and N2O molecule. his approach opens the path for high fidelity multidimensional spectroscopy with attosecond pulses.

#P1-38, Photodissociation dynamics of NO2 probed with single harmonics from an XUV monochromator, A. VON CONTA AND H. J. WÖRNER, A time-preserving XUV/VUV monochromator for HHG [1] is used to investigate the photodissociation dynamics of NO2 by photo-electron kinetic energy measurements in a magnetic-bottle time-of-flight spectrometer [2]. Upon pumping the system optically with 3.1 eV (400 nm) pulses of ~40fs duration the molecule is excited to the