93 research outputs found
Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields
No full textCitation: Li, H., Mignolet, B., Wachter, G., Skruszewicz, S., Zherebtsov, S., Sussmann, F., . . . Kling, M. F. (2015). Coherent Electronic Wave Packet Motion in C-60 Controlled by the Waveform and Polarization of Few-Cycle Laser Fields. Physical Review Letters, 114(12), 6. doi:10.1103/PhysRevLett.114.123004Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C-60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.Additional Authors: Tiggesbaumker, J.;Meiwes-Broer, K. H.;Lemell, C.;Burgdorfer, J.;Levine, R. D.;Remacle, F.;Kling, M. F
Probing the high latitude ionosphere from ground-based observations: The state of current knowledge and capabilities during IPY (2007-2009)
No full textDuring the International Polar Year (IPY), one area of great interest is co-coordinated, multi-instrument probing of the ionosphere at high latitudes. This region is important not only for the applications that rely upon our understanding of it, but also because it contains the footprints of processes that have their origin in the interplanetary space. Many different techniques are now available for probing the ionosphere, from radar measurements to the analysis of very low frequency (VLF) wave paths. Combining these methods provides the ability to study the ionosphere from high in the F-region to the bottom of the D-layer. Thus, coupling processes from the magnetosphere and to the neutral atmosphere can be considered. An additional dimension is through comparisons of the response of the two polar ionospheres to similar (or the same) geomagnetic activity. With more instruments available at the South Pole inter-hemispheric, studies have become easier to accomplish such that a fuller picture of the global response to Sun-Earth coupling can be painted. This paper presents a review of the current state of knowledge in ionospheric probing. It cannot provide a comprehensive guide of the work to date due to the scale of the topic. Rather it is intended to give an overview of the techniques and recent results from some of the instruments and facilities that are a part of the IPY cluster 63-Heliosphere Impact on Geospace. In this way it is hoped that the reader will gain a flavor of the recent research performed in this area and the potential for continuing collaboration and capabilities during the IP
Attosecond control of electron localization in one- and two-color dissociative ionization of H2 and D2
No full textWe present one-color (IR) and two-color (single attosecond XUV pulse + IR) experiments where the sub-cycle evolution of the electric field of light is used to control the dissociative ionization of hydrogen and deuterium molecules
Attosecond control of electron localization in one- and two-color dissociative ionization of H2 and D2
No full textWe report experiments where an attosecond pulse launches a wavepacket on the dissociative state of D2 +, and a few-cycle IR pulse localizes the electron on one ionic fragment with attosecond sensitivity to the XUV-IR delay
Attosecond electron interferometryCLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference
No full textAttosecond Electron Spectroscopy Using a Novel Interferometric Pump-Probe Technique
No full textAttosecond electron spectroscopy using a novel interferometric pump-probe techniqu
Attosecond excitation of electron wavepackets2008 Conference on Lasers and Electro-Optics
No full textWe present experiments, supported by time-dependent Schrödinger simulations, on the dynamics of Helium bound states after an attosecond excitation in the presence of a strong infrared laser field
Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres
No full textCitation: Sussmann, F., Seiffert, L., Zherebtsov, S., Mondes, V., Stierle, J., Arbeiter, M., . . . Fennel, T. (2015). Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres. Nature Communications, 6, 9. doi:10.1038/ncomms8944Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena
Attosecond chronoscopy of electron scattering in dielectric nanoparticles
No full textThe scattering of electrons in dielectric materials is central to laser nanomachining, light-driven electronics and radiation damage. Here, we demonstrate real-time access to electron scattering by implementing attosecond streaking spectroscopy on dielectric nanoparticles: photoelectrons are generated inside the nanoparticles and both their transport through the material and photoemission are tracked on an attosecond timescale. We develop a theoretical framework for attosecond streaking spectroscopy in dielectrics and identify that the presence of the internal field inside the material cancels the influence of elastic scattering, enabling the selective characterization of the inelastic scattering time. The approach is demonstrated on silica nanoparticles, where an inelastic mean-free path is extracted for 20–30 eV. Our approach enables the characterization of inelastic scattering in various dielectric solids and liquids, including water, which can be studied in the form of droplets
Femtosecond time-resolved spectroscopy in polyatomic systems investigated by velocity-map imaging and high-order harmonic generation
No full textDans cette thèse, la dynamique de photodissociation de l'azoture de chlore (ClN3) est étudiée dans le domaine temporel par imagerie de vecteur vitesse des photofragments, spécialement du chlore et de N3. Cette imagerie résolue à l'échelle femtoseconde permet d'extraire les temps de dissociation, l'établissement temporel de la balance d'énergie de la réaction ainsi que la conservation des moments. Cette étude a permis de différencier deux domaines d'énergie: l'un menant à la formation d'un fragment N3 linéaire (étude autour de 4.5 eV d'excitation électronique) et le plus intéressant aboutissant à la formation d'un fragment N3 cyclique (autour de 6 eV).
Dans une seconde étude, la dynamique de relaxation électronique du tétrathiafulvalène (C6H4S4-TTF) est étudiée autour de 4 eV par spectroscopie de masse résolue en temps ainsi que par spectroscopie de photoélectron. Les seuils d'ionisation dissociative sont extraits d'une détection en coïncidence entre les photoélectrons de seuil et les fragments ionisés réalisée sur rayonnement synchrotron.
Les deux dernières expériences sont basées sur la génération d'harmoniques d'ordre élevé dans l'XUV d'une impulsion femtoseconde à 800 nm ou à 400 nm. Dans la première expérience, les harmoniques sont couplées à un imageur de vecteur vitesse en tant que rayonnement secondaire VUV. Par imagerie de photoélectron résolue en temps, nous avons révélé ainsi les dynamiques de relaxation des états de Rydberg initiée par une impulsion femtoseconde XUV à 15.5 eV dans l'argon et à 9.3 eV dans l'acétylène. Dans la seconde expérience, couramment nommée spectroscopie attoseconde, les harmoniques constituent le signal pompe sonde. Deux types de spectroscopie attoseconde ont été réalisés pour étudier la dynamique vibrationnelle de SF6: une expérience en réseau transitoire créé par deux impulsions pompe Raman avec une impulsion sonde intense générant les harmoniques à partir du réseau d'excitation et une expérience d'interférence de deux rayonnement XUV en champ lointain créés par deux impulsions sonde intensesRevealing the underlying ultrafast dynamics in molecular reaction spectroscopy demands state-of-the-art imaging techniques to follow a molecular process step by step.
Femtosecond time-resolved velocity-map imaging is used to study the photodissociation dynamics of chlorine azide (ClN3). Here especially the co-fragments chlorine and N3 are studied on the femtosecond timescale in two excitation energy regions around 4.67 eV and 6.12 eV, leading to the formation of a linear N3 fragment and a cyclic N3 fragment, respectively. This work is the first femtosecond spectroscopy study revealing the formation of cyclic N3. Tetrathiafulvalene (TTF, C6H4S4) electronic relaxation is studied, while scanning the electronic excitation around 4 eV, by time resolved mass and photoelectron spectroscopy. As only few is known about the ion continuum about TTF the imaging photoelectron photoion coincidence (iPEPICO) technique is used in order to disentangle the complex ionic dissociation. The second part of the thesis is based on the generation and application of XUV light pulses by high-order harmonic generation with an intense femtosecond laser pulse in a molecular target. Two types of phase sensitive attosecond spectroscopy experiments were conducted to study the vibrational dynamics of SF6: one using strong field transient grating spectroscopy, where high-order harmonic generation takes place in a grating of excitation, and the second experiment using high-order harmonic interferometry using two intense XUV probe pulses. The temporal dependencies in phase and amplitude reveal the vibrational dynamics in SF6 and demonstrate that high-order harmonic generation is sensitive to the internal excitations. Last but not least, the use of high-order harmonics as a XUV photon source for the velocity-map imaging spectrometer is investigated. Using time-resolved photoelectron imaging, the relaxation dynamics initiated with 15.5 eV in argon and 9.3 eV in acetylene are reveale
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