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Jiancai Xu, Baifei Shen, Xiaomei Zhang, Yin Shi, Liangliang Ji, Lingang Zhang, Tongjun Xu, Wenpeng Wang, Xueyan Zhao, Zhizhan Xu
Extreme-ultravoilet (XUV) attosecond pulses with durations of a few tens of attosecond have been successfully applied for exploring ultrafast electron dynamics at the atomic scale. But their weak intensities limit the further application in demonstrating nonlinear responses of inner-shell electrons. Optical attosecond pulses will provide sufficient photon flux to initiate strong-field processes. Here we proposed a novel method to generate an ultra-intense isolated optical attosecond pulse through relativistic multi-cycle laser pulse interacting with a designed gas-foil target...
February 8, 2018: Scientific Reports
Johannes Passig, Sergey Zherebtsov, Robert Irsig, Mathias Arbeiter, Christian Peltz, Sebastian Göde, Slawomir Skruszewicz, Karl-Heinz Meiwes-Broer, Josef Tiggesbäumker, Matthias F Kling, Thomas Fennel
The original PDF version of this Article contained an error in Equation 1. The original HTML version of this Article contained errors in Equation 2 and Equation 4. These errors have now been corrected in both the PDF and the HTML versions of the Article.
February 7, 2018: Nature Communications
Kaijun Yuan, Andre Dieter Bandrauk
Charge migration is a fundamental and important process in the photo-chemistry of molecules which has been explored by time-resolved photoelectron angular distributions. A scheme based on UV pump and polarized soft x-ray probe techniques shows that photoelectron diffraction effects enable us to reconstruct electronic coherences encoding the information of the charge migration with extreme time resolutions. We discuss how probe pulse helicity influences the probing photoelectron spectra in the presence of molecular nonspherical Coulomb potentials...
February 6, 2018: Journal of Physical Chemistry. A
Meng Li, Guizhong Zhang, Xuelian Kong, Tianqing Wang, Xin Ding, Jianquan Yao
In this paper, we report our numerical simulation on the symmetry distortion and mechanism of the vortex-shaped momentum distribution of hydrogen atom by taking into account of the dynamic Stark effect. By deploying the strong field approximation (SFA) theory, we performed extensive simulation on the momentum pattern of hydrogen ionized by two time-delayed oppositely circularly polarized attosecond pulses. We deciphered that this distortion is originated from the temporal characteristics of the dynamic Stark phase which is nonlinear in time...
January 22, 2018: Optics Express
Chunyang Zhai, Xiaofan Zhang, Xiaosong Zhu, Lixin He, Yinfu Zhang, Baoning Wang, Qingbin Zhang, Pengfei Lan, Peixiang Lu
Molecular orbital tomography (MOT) based on high-order-harmonic generation opens a way to track the molecular electron dynamics or even follow a chemical reaction. However, the real-time imaging of the evolution of electron orbitals is hampered by the multi-shot measurement of high-order harmonics. Here, we report a single-shot MOT scheme with orthogonal two-color (OTC) fields. This scheme enables the tomographic imaging of molecular orbital with single-shot measurement in experiment, owing to the two-dimensional manipulation of the electron motion in OTC fields...
February 5, 2018: Optics Express
E Conejero Jarque, J San Roman, F Silva, R Romero, W Holgado, M A Gonzalez-Galicia, B Alonso, I J Sola, H Crespo
Gas-filled hollow-core fiber (HCF) pulse post-compressors generating few- to single-cycle pulses are a key enabling tool for attosecond science and ultrafast spectroscopy. Achieving optimum performance in this regime can be extremely challenging due to the ultra-broad bandwidth of the pulses and the need of an adequate temporal diagnostic. These difficulties have hindered the full exploitation of HCF post-compressors, namely the generation of stable and high-quality near-Fourier-transform-limited pulses. Here we show that, independently of conditions such as the type of gas or the laser system used, there is a universal route to obtain the shortest stable output pulse down to the single-cycle regime...
February 2, 2018: Scientific Reports
Marieke F Jager, Christian Ott, Christopher J Kaplan, Peter M Kraus, Daniel M Neumark, Stephen R Leone
We present an extreme ultraviolet (XUV) transient absorption apparatus tailored to attosecond and femtosecond measurements on bulk solid-state thin-film samples, specifically when the sample dynamics are sensitive to heating effects. The setup combines methodology for stabilizing sub-femtosecond time-resolution measurements over 48 h and techniques for mitigating heat buildup in temperature-dependent samples. Single-point beam stabilization in pump and probe arms and periodic time-zero reference measurements are described for accurate timing and stabilization...
January 2018: Review of Scientific Instruments
Angela Parise, Aurelio Alvarez-Ibarra, Xiaojing Wu, Xiaodong Zhao, Julien Pilmé, Aurélien de la Lande
We report original analyses of attosecond electron dynamics of molecules subject to collisions by high energy charged particles based on Real-Time Time-Dependent-Density-Functional-Theory simulations coupled to Topological Analyses of the Electron Localization Function (TA-TD-ELF). We investigate irradiation of water and guanine. TA-TD-ELF enables qualitative and quantitative characterizations of bond breaking and formation, of charge migration within topological basins, or of electron attachment to the colliding particle...
January 31, 2018: Journal of Physical Chemistry Letters
Markus Klinker, Carlos Marante, Luca Argenti, Jesús González-Vázquez, Fernando Martin
Direct measurement of autoionization lifetimes by using time-resolved experimental techniques is a promising approach when energy-resolved spectroscopic methods do not work. Attosecond time-resolved experiments have recently provided the first quantitative determination of autoionization lifetimes of the lowest members of the well-known Hopfield series of resonances in N2. In this work, we have used the recently developed XCHEM approach to study photoionization of the N2 molecule in the vicinity of these resonances...
January 24, 2018: Journal of Physical Chemistry Letters
M P Tooley, B Ersfeld, S R Yoffe, A Noble, E Brunetti, Z M Sheng, M R Islam, D A Jaroszynski
Self-injection in a laser-plasma wakefield accelerator is usually achieved by increasing the laser intensity until the threshold for injection is exceeded. Alternatively, the velocity of the bubble accelerating structure can be controlled using plasma density ramps, reducing the electron velocity required for injection. We present a model describing self-injection in the short-bunch regime for arbitrary changes in the plasma density. We derive the threshold condition for injection due to a plasma density gradient, which is confirmed using particle-in-cell simulations that demonstrate injection of subfemtosecond bunches...
July 28, 2017: Physical Review Letters
Alexander H Winney, Suk Kyoung Lee, Yun Fei Lin, Qing Liao, Pradip Adhikari, Gihan Basnayake, H Bernhard Schlegel, Wen Li
With a novel three-dimensional electron-electron coincidence imaging technique and two-electron angular streaking method, we show that the emission time delay between two electrons can be measured from tens of attoseconds to more than 1 fs. Surprisingly, in benzene, the double ionization rate decays as the time delay between the first and second electron emission increases during the first 500 as. This is further supported by the decay of the Coulomb repulsion in the direction perpendicular to the laser polarization...
September 22, 2017: Physical Review Letters
Hans Jakob Wörner, Christopher A Arrell, Natalie Banerji, Andrea Cannizzo, Majed Chergui, Akshaya K Das, Peter Hamm, Ursula Keller, Peter M Kraus, Elisa Liberatore, Pablo Lopez-Tarifa, Matteo Lucchini, Markus Meuwly, Chris Milne, Jacques-E Moser, Ursula Rothlisberger, Grigory Smolentsev, Joël Teuscher, Jeroen A van Bokhoven, Oliver Wenger
The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer...
November 2017: Structural Dynamics (Melville, N.Y.)
Inga S Ulusoy, Zachary Stewart, Angela K Wilson
With the recent advances in experimental attosecond science, theoretical predictions of electron dynamics can now be validated against experiment. Time-dependent studies of the electron motion in molecules can be used to obtain information about electronic transitions and the interaction of the electrons with electromagnetic fields. Often, these approaches rely on single-excited wave functions. Presented here is a first attempt to evaluate the accuracy of the time-dependent configuration interaction method so that the optimal representation of the electronic wave function for time-dependent studies can be assessed...
January 7, 2018: Journal of Chemical Physics
K Hu, H-C Wu
A novel scheme for generating a pair of gigawatt attosecond pulses by coherent Thomson scattering from relativistic electron sheets is proposed. With a circularly polarized relativistic laser pulse, the scattered x-ray signal can have a saddlelike temporal profile, where the lower electromagnetic frequencies are found mostly in the center region of this saddlelike profile. By filtering out the latter, we can obtain two few-attosecond pulses separated by a subfemtosecond interval, which is tunable by controlling the energy of the sheet electrons...
December 22, 2017: Physical Review Letters
C Brée, M Hofmann, A Demircan, U Morgner, O Kosareva, A Savel'ev, A Husakou, M Ivanov, I Babushkin
The ionization rate of an atom in a strong optical field can be resonantly enhanced by the presence of long-living atomic levels (so-called Freeman resonances). This process is most prominent in the multiphoton ionization regime, meaning that the ionization event takes many optical cycles. Nevertheless, here, we show that these resonances can lead to rapid subcycle-scale plasma buildup at the resonant values of the intensity in the pump pulse. The fast buildup can break the cycle-to-cycle symmetry of the ionization process, resulting in the generation of persistent macroscopic plasma currents which remain after the end of the pulse...
December 15, 2017: Physical Review Letters
Enikoe Seres, Jozsef Seres, Shinichi Namba, John Afa, Carles Serrat
Applying extreme ultraviolet (XUV) transient absorption spectroscopy, the dynamics of the two laser dressed transitions 3d5/2-to-5p3/2 and 3p3/2-to-5s1/2 at photon energies of 91.3 eV and 210.4 eV were examined with attosecond temporal resolution. The dressing process was modeled with density matrix equations which are found to describe very accurately both the experimentally observed transmission dynamics and the linear and nonlinear dressing oscillations at 0.75 PHz and 1.5 PHz frequencies. Furthermore, using Fourier transform XUV spectroscopy, quantum beats from the 3d5/2-3d3/2 and 3p3/2-3p1/2 sublevels at 0...
December 11, 2017: Optics Express
F Labaye, M Gaponenko, V J Wittwer, A Diebold, C Paradis, N Modsching, L Merceron, F Emaury, I J Graumann, C R Phillips, C J Saraceno, C Kränkel, U Keller, T Südmeyer
We demonstrate a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) driven directly inside the cavity of a mode-locked thin-disk laser oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and a 17.35 MHz repetition rate. We drive HHG in a high-pressure xenon gas jet with an intracavity peak intensity of 2.8×1013  W/cm2 and 320 W of intracavity average power. Despite the high-pressure gas jet, the laser operates at high stability...
December 15, 2017: Optics Letters
M Kübel, Z Dube, A Yu Naumov, M Spanner, G G Paulus, M F Kling, D M Villeneuve, P B Corkum, A Staudte
Ionization of an atom or molecule by a strong laser field produces suboptical cycle wave packets whose control has given rise to attosecond science. The final states of the wave packets depend on ionization and deflection by the laser field, which are convoluted in conventional experiments. Here, we demonstrate a technique enabling efficient electron deflection, separate from the field driving strong-field ionization. Using a midinfrared deflection field permits one to distinguish electron wave packets generated at different field maxima of an intense few-cycle visible laser pulse...
November 3, 2017: Physical Review Letters
Ryoichi Hajima, Ryoji Nagai
We propose a scheme to generate carrier-envelope-phase (CEP) stabilized few-cycle optical pulses from a free-electron laser oscillator. The CEP stabilization is realized by the continuous injection of CEP-stabilized seed pulses from an external laser to the free-electron laser oscillator whose cavity length is perfectly synchronized to the electron bunch repetition. Operated at a midinfrared wavelength, the proposed method is able to drive a photon source based on high harmonic generation (HHG) to explore the generation of isolated attosecond pulses at photon energies above 1 keV with a repetition of >10  MHz...
November 17, 2017: Physical Review Letters
Denitsa Baykusheva, Simon Brennecke, Manfred Lein, Hans Jakob Wörner
High-harmonic spectroscopy driven by circularly polarized laser pulses and their counterrotating second harmonic is a new branch of attosecond science which currently lacks quantitative interpretations. We extend this technique to the midinfrared regime and record detailed high-harmonic spectra of several rare-gas atoms. These results are compared with the solution of the Schrödinger equation in three dimensions and calculations based on the strong-field approximation that incorporate accurate scattering-wave recombination matrix elements...
November 17, 2017: Physical Review Letters
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