Publications
241 results found
Smirnova O, Patchkovskii S, Mairesse Y, et al., 2009, Strong-field control and spectroscopy of attosecond electron-hole dynamics in molecules, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 106, Pages: 16556-16561, ISSN: 0027-8424
Molecular structures, dynamics and chemical properties are determined by shared electrons in valence shells. We show how one can selectively remove a valence electron from either Pi vs. Sigma or bonding vs. nonbonding orbital by applying an intense infrared laser field to an ensemble of aligned molecules. In molecules, such ionization often induces multielectron dynamics on the attosecond time scale. Ionizing laser field also allows one to record and reconstruct these dynamics with attosecond temporal and sub-Angstrom spatial resolution. Reconstruction relies on monitoring and controlling high-frequency emission produced when the liberated electron recombines with the valence shell hole created by ionization.
Zheltikov AM, Voronin AA, Kitzler M, et al., 2009, Optical detection of interfering pathways in subfemtosecond multielectron dynamics., Phys Rev Lett, Vol: 103, Pages: 033901-033901, ISSN: 0031-9007
We show how time-resolved coherent anti-Stokes Raman scattering can be used to identify interfering pathways in the relaxation dynamics of autoionizing transients in many-electron systems, on femto- and attosecond time scales. For coherent population of many states, autoionizing wave-packet dynamics is resolved. We identify bound-bound, continuum-bound, and bound-continuum-bound contributions and show that they leave distinct features in the total coherent anti-Stokes Raman scattering signal.
Krausz F, Ivanov M, 2009, Attosecond physics, REVIEWS OF MODERN PHYSICS, Vol: 81, Pages: 163-234, ISSN: 0034-6861
Intense ultrashort light pulses comprising merely a few wave cycles became routinely available by the turn of the millennium. The technologies underlying their production and measurement as well as relevant theoretical modeling have been reviewed in the pages of Reviews of Modern Physics (Brabec and Krausz, 2000). Since then, measurement and control of the subcycle field evolution of few-cycle light have opened the door to a radically new approach to exploring and controlling processes of the microcosm. The hyperfast-varying electric field of visible light permitted manipulation and tracking of the atomic-scale motion of electrons. Striking implications include controlled generation and measurement of single attosecond pulses of extreme ultraviolet light as well as trains of them, and real-time observation of atomic-scale electron dynamics. The tools and techniques for steering and tracing electronic motion in atoms, molecules, and nanostructures are now becoming available, marking the birth of attosecond physics. In this article these advances are reviewed and some of the expected implications are addressed.
Sukiasyan S, McDonald C, Van Vlack C, et al., 2009, Signatures of bound-state-assisted nonsequential double ionization, PHYSICAL REVIEW A, Vol: 80, ISSN: 1050-2947
The time-dependent multiconfiguration Hartree method is optimized for intense laser dynamics and applied to nonsequential double ionization in a two-electron diatomic model molecule with two dimensions per electron. The efficiency of our method brings these calculations from the realm of large scale computation facilities to single processor machines. The resulting two-electron spectrum exhibits pronounced signatures from which the ionic bound states involved in nonsequential double ionization are retrieved with the help of a semiclassical model. A mechanism for the ionization dynamics is suggested.
Sukiasyan S, McDonald C, Van Vlack C, et al., 2009, Correlated few-electron dynamics in intense laser fields, CHEMICAL PHYSICS, Vol: 366, Pages: 37-45, ISSN: 0301-0104
The time-dependent multi-configuration Hartree method is applied to nonsequential double ionization and to high harmonic generation and molecular tomography in a two-electron diatomic model molecule with two-dimensions per electron. The efficiency of our method brings these calculations from the realm of large scale computation facilities to single processor machines. The resulting two-electron spectrum exhibits pronounced signatures from which the ionic bound states involved in nonsequential double ionization are retrieved with the help of a semi-classical model. A mechanism for the ionization dynamics is suggested. In HHG, all relevant multi-electron effects are identified and quantified and their implications on molecular tomography are discussed. (C) 2009 Elsevier B.V. All rights reserved.
Staudte A, Patchkovskii S, Pavicic D, et al., 2009, Angular Tunneling Ionization Probability of Fixed-in-Space H-2 Molecules in Intense Laser Pulses, PHYSICAL REVIEW LETTERS, Vol: 102, ISSN: 0031-9007
We propose a new approach to obtain molecular frame photoelectron angular distributions from molecules ionized by intense laser pulses. With our method we study the angular tunnel ionization probability of H-2 at a wavelength of 800 nm over an intensity range of 2-4.5x10(14) W/cm(2). We find an anisotropy that is stronger than predicted by any existing model. To explain the observed anisotropy and its strong intensity dependence we develop an analytical model in the framework of the strong-field approximation. It expresses molecular ionization as a product of atomic ionization rate and a Fourier transform of the highest occupied molecular orbital filtered by the strong-field ionization process.
Smirnova O, Mairesse Y, Patchkovskii S, et al., 2009, High harmonic interferometry of multi-electron dynamics in molecules, NATURE, Vol: 460, Pages: 972-977, ISSN: 0028-0836
High harmonic emission occurs when an electron, liberated from a molecule by an incident intense laser field, gains energy from the field and recombines with the parent molecular ion. The emission provides a snapshot of the structure and dynamics of the recombining system, encoded in the amplitudes, phases and polarization of the harmonic light. Here we show with CO2 molecules that high harmonic interferometry can retrieve this structural and dynamic information: by measuring the phases and amplitudes of the harmonic emission, we reveal ’fingerprints’ of multiple molecular orbitals participating in the process and decode the underlying attosecond multi-electron dynamics, including the dynamics of electron rearrangement upon ionization. These findings establish high harmonic interferometry as an effective approach to resolving multi-electron dynamics with sub-Angstrom spatial resolution arising from the de Broglie wavelength of the recombining electron, and attosecond temporal resolution arising from the timescale of the recombination event.
Graefe S, Engel V, Ivanov MY, 2008, Attosecond photoelectron spectroscopy of electron tunneling in a dissociating hydrogen molecular ion, PHYSICAL REVIEW LETTERS, Vol: 101, ISSN: 0031-9007
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Ivanov MY, Yakovlev V, Krausz F, 2008, Opportunities for mid-IR sources in intense-field and attosecond physics, Mid-Infrared Coherent Sources and Applications, Editors: Ebrahim-Zadeh, Sorokina, Publisher: Springer Verlag, ISBN: 9781402064395
This volume represents a collection of authoritative reviews by internationallyrecognized experts in the field of middle infrared (mid-IR) coherent sources and ...
Smirnova O, Spanner M, Ivanov M, 2008, Analytical solutions for strong field-driven atomic and molecular one- and two-electron continua and applications to strong-field problems, PHYSICAL REVIEW A, Vol: 77, ISSN: 1050-2947
We develop the eikonal-Volkov approximation (EVA) to describe atomic and molecular strong-field dynamics. The main component of this approach is the approximate solution for the continuum states of one and two electrons in the presence of a long-range ionic potential and a strong laser field. These solutions include the laser field fully, the ionic potential, and the electron-electron interaction in the eikonal approximation, and describe the nonperturbative coupling between these interactions. Comparison with numerically evaluated continuum electron wave functions demonstrates quantitative accuracy of the approximate solutions. Their long-time limit yields the quasienergy (Floquet) states of the continuum electron. We also show how to extend the applicability of these solutions to deal with the singularities of the ionic potential, where straightforward eikonal approximation breaks down. The large-angle scattering (hard collision) is incorporated in the EVA formalism using an expansion in the number of hard collisions. Finally, we describe how the EVA formalism can be used to obtain simple analytical expressions for various strong-field problems.
Murray R, Ivanov M, 2008, Two-color control of laser induced electron diffraction, JOURNAL OF MODERN OPTICS, Vol: 55, Pages: 2513-2525, ISSN: 0950-0340
We present an analysis using intense, few-cycle two-color laser pulses to image the structure of small molecules with nearly 1 fs temporal and sub- spatial resolution. We perform analytical calculations using S-matrix techniques to obtain laser-induced electron diffraction images of a diatomic molecule. The two-color field allows us to control recollision through the combination of two-color gating and polarization gating. By tuning the parameters of the two-color field we reduce the recollision to a single event, obtaining cleaner image and significantly improving time-resolution. In this paper we examine a 5 fs FWHM pulse with the second color omega(2) = 1.5 omega(1).
Grafe S, Ivanov MY, 2008, On the electron localization dynamics induced by laser-driven electronic rescattering, JOURNAL OF MODERN OPTICS, Vol: 55, Pages: 2557-2572, ISSN: 0950-0340
We apply our recently developed approach [Grafe, S.; Ivanov, M.Y. Phys. Rev. Lett. 2007, 99, 163603] describing correlated two-electron dynamics in strong laser fields to the description of laser-induced recollision between an electron and its parent molecular ion. We present the derivation for an effective interaction potential which describes the effect of the laser-driven electron collision while retaining the correlation between the colliding and the bound electron. Using dissociative ionization of molecular hydrogen as an example, we analyze details of the dynamics of correlation-driven electron localization in a dissociating hydrogen molecular ion.
Mairesse Y, Dudovich N, Levesque J, et al., 2008, Electron wavepacket control with elliptically polarized laser light in high harmonic generation from aligned molecules, NEW JOURNAL OF PHYSICS, Vol: 10, ISSN: 1367-2630
We study experimentally and theoretically the high harmonic emission from aligned samples of nitrogen and carbon dioxide, in an elliptically polarized laser field. The ellipticity induces a lateral shift of the recombining electron wavepacket in the generation process. We show that this effect, which is well known from high harmonic generation (HHG) in atoms, can be useful to maintain the plane wave approximation in the case of HHG from molecules whose orbitals contain nodal planes. The study of the harmonic signal as a function of molecular alignment also reveals the role of the ellipticity on the recollision angle of the electron wavepacket, which can be used to accurately track the position of resonances in harmonic spectra.
Grafe S, Engel V, Ivanov MY, 2008, Attosecond photoelectron spectroscopy of electron tunneling in a dissociating hydrogen molecular ion, PHYSICAL REVIEW LETTERS, Vol: 101, ISSN: 0031-9007
We demonstrate the potential of intense-field pump, attosecond probe photoelectron spectroscopy to monitor electron tunneling between the two protons during dissociative ionization of the hydrogen molecule, with attosecond temporal and Angstrom-scale spatial resolution.
Ivanov MY, Marangos JP, 2007, Time-resolved imaging of atomic-scale electron and nuclear dynamics, JOURNAL OF MODERN OPTICS, Vol: 54, Pages: 899-903, ISSN: 0950-0340
Dudovich N, Smirnova O, Mairesse Y, et al., 2007, Ultrafast phenomena XV, Ultrafast phenomena XV, Editors: Corkum, Publisher: Springer Verlag, ISBN: 9783540687795
This book summarizes the results presented at the 15th International Conference on Ultrafast Phenomena and provides an up-to-date view of this important and ...
Marangos J, Ivanov MY, 2007, Ultrafast Dynamic Imaging of Matter, special issue of Journal of Modern Optics, Publisher: Talyor & Francis
Dietzek B, Grafe S, Schmitt M, et al., 2007, Experimental observation of different-order components of a vibrational wave packet in a bulk dielectric using high-order Raman scattering, PHYSICAL REVIEW LETTERS, Vol: 98, ISSN: 0031-9007
We use high-order Raman scattering in a bulk dielectric to characterize coherent dynamics with precision typical for gas phase experiments. The experimental pump-probe approach allows for the simultaneous observation and separation in space and time of the individual contributions of different-order Raman processes to a coherent wave packet without relying on phase-matching conditions and within the same experimental geometry. We propose a novel technique to discriminate between stimulated excitation of vibronic levels in the impulsive and intermediate excitation regimes, futhermore allowing us to distinguish between different pathways contributing to the same fifth-order Raman processes.
Smirnova O, Mouritzen AS, Patchkovskii S, et al., 2007, Coulomb-laser coupling in laser-assisted photoionization and molecular tomography, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 40, Pages: F197-F206, ISSN: 0953-4075
Using the example of laser-assisted photoionization, we analyse the interplay of an intense laser field and the atomic/molecular potential during the electron motion after ionization. We give conditions to determine when the electron’s oscillations in the strong laser field are approximately decoupled from its acceleration in the ionic potential, and when they are not. Excellent agreement between analytical and numerical results allows us to assess the recipes for analysing interference structures in high harmonic generation in molecules.
Dudovich N, Smirnova O, Levesque J, et al., 2007, Measurement and control of attosecond pulse formation, 15th International Conference on Ultrafast Phenomena, Publisher: SPRINGER-VERLAG BERLIN, Pages: 21-+, ISSN: 0172-6218
Grafe S, Ivanov MY, 2007, Effective fields in laser-driven electron recollision and charge localization, PHYSICAL REVIEW LETTERS, Vol: 99, ISSN: 0031-9007
We propose a model to describe correlated two-electron dynamics in strong laser fields during laser-induced recollision between an electron and its parent ion. We derive an effective interaction potential which describes the effect of the laser-driven electron collision with an ion while retaining the correlation between the colliding and the bound electron. Using dissociative ionization of molecular hydrogen as an example, we analyze the dynamics of correlation-driven electron localization in a dissociating hydrogen molecular ion.
Yakovlev VS, Ivanov M, Krausz F, 2007, Enhanced phase-matching for generation of soft X-ray harmonics and attosecond pulses in atomic gases, OPTICS EXPRESS, Vol: 15, Pages: 15351-15364, ISSN: 1094-4087
We theoretically investigate the generation of high harmonics and attosecond pulses by mid-infrared (IR) driving fields. Conditions for coherent build-up of high harmonics are revisited. We show that the coherence length dictated by ionization-induced dephasing does not constitute an ultimate limitation to the coherent growth of soft X-ray (> 100 eV) harmonics driven by few-cycle mid-IR driving pulses: perfect phase-matching, similar to non-adiabatic self-phase-matching, can be achieved even without non-linear deformation of the driving pulse. Our trajectory-based analysis of phase-matching reveals several important advantages of using longer laser wavelengths: conversion efficiency can be improved by orders of magnitude, phase-matched build-up of harmonics can be achieved in a jet with a high gas pressure, and isolated attosecond pulses can be extracted from plateau harmonics. (c) 2007 Optical Society of America.
Shapiro EA, Walmsley IA, Ivanov MY, 2007, Suppression of decoherence in a wave packet via nonlinear resonance., Phys Rev Lett, Vol: 98, Pages: 050501-050501, ISSN: 0031-9007
We propose a simple approach for suppressing decoherence of a wave packet excited in an anharmonic oscillator. We show that when a resonant external field forces the oscillator to follow the driving force, motion around the resonant trajectory inside a stable resonant island can be made almost completely immune to the environment. As an example, we study suppression of decoherence due to coupling to thermally populated rotations in vibrational wave packets in a Na2 molecule.
Smirnova O, Spanner M, Ivanov M, 2007, Anatomy of strong field ionization II: to dress or not to dress?, JOURNAL OF MODERN OPTICS, Vol: 54, Pages: 1019-1038, ISSN: 0950-0340
We analyse S-matrix-type approaches to strong-field ionization by an intense few-cycle laser pulse. We derive simple modi. cations of approximate S-matrix-type approaches that either neglect the effect of the ionic potential after ionization, or treat this potential perturbatively. We show how these modi. cations eliminate some crucial problems and artefacts, such as the ’curse of the displaced atom’, associated with the choice of gauge in the strong field approximation. We then discuss how these approximate S-matrix-type approaches should be applied to dissociating molecules using the example of H-2(+). We show that suppression of electron tunnelling between the two fragments of the molecular ion introduces dramatic changes in the spectrum of high harmonic emission generated by an intense laser pulse that probes the molecular dissociation. For large internuclear distances and even when the active electron is fully delocalized between the two fragments, the high harmonic spectrum loses all traces of the conventional interference pattern associated with a two-centre molecular structure.
Shapiro EA, Spanner M, Ivanov MY, 2007, Wave packets in a sieve: quantum control at the edge of strong chaos, JOURNAL OF MODERN OPTICS, Vol: 54, Pages: 2161-2176, ISSN: 0950-0340
We consider the quantum dynamics of the kicked rotor model in the regime where the last stable resonance islands in the classical phase space disappear. It is found that phase space regions with lower local diffusion rates are able to preserve quantum population. The low-diffusion regions can be moved through phase space in a quasi-adiabatic way by smoothly varying the parameters of the kicking field. With appropriately chosen time-scales for the variation of the field parameters, wave packets initially localized around the low-diffusion areas remain localized around these regions as the regions are moved. The wave packets can then be carried to desired regions of space despite the predominantly chaotic character of the classical phase space. We also comment on the Gong-Brumer scenario of coherent control of quantum chaotic diffusion [Phys. Rev. Lett. 86 1741 (2001)]. While our phase-space inspired control has a clear semiclassical interpretation, it appears that the Gong-Brumer control has a predominantly quantum origin. Furthermore, it is found that our control over wave packet localization disappears in the deeply chaotic regime, while the Gong-Brumer control over the chaotic diffusion persists in this regime but becomes increasingly unstable with increasing chaoticity.
Dudovich N, Smirnova O, Mairesse Y, et al., 2006, Control and Measurement of Attosecond pulses, 2006 IEEE LEOS Annual Meeting Conference Proceedings, Vols 1 and 2, Publisher: IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA
Corkum PB, Ivanov MY, 2006, "Multiphoton Processes", special issue of the Journal of Physics B: Atomic, Molecular and Optical Physics, Publisher: IOP
Dudovich N, Smirnova O, Levesque J, et al., 2006, Measuring and controlling the birth of attosecond XUV pulses, NATURE PHYSICS, Vol: 2, Pages: 781-786, ISSN: 1745-2473
Generating attosecond pulses has required a radically different approach from previous ultrafast optical methods. The technology of attosecond measurement, however, is built on established methods of characterizing femtosecond pulses: the pulse is measured after it has left the region where it was produced. We offer a completely different approach: in situ measurement. That is, we integrate attosecond-pulse production and measurement in a manner that can be applied to many high-order nonlinear interactions. To demonstrate this approach, we combine a low-intensity (<10(-3)) second-harmonic beam with the fundamental beam, to gently perturb the production process without significantly modifying it. The attosecond-pulse duration is read from the modulation of the even-harmonic signal as a function of the two-field delay. Increasing the second-harmonic intensity slightly (<10(-2)), we extend measurement to control. We demonstrate control by manipulating the high-harmonic spectrum with high efficiency.
Dudovich N, Levesque J, Smirnova O, et al., 2006, Attosecond temporal gating with elliptically polarized light, PHYSICAL REVIEW LETTERS, Vol: 97, ISSN: 0031-9007
Temporal gating allows high accuracy time-resolved measurements of a broad range of ultrafast processes. By manipulating the interaction between an atom and an intense laser field, we extend gating into the nonlinear medium in which attosecond optical and electron pulses are generated. Our gate is an amplitude gate induced by ellipticity of the fundamental pulse. The gate modulates the spectrum of the high harmonic emission and we use the measured modulation to characterize the sub-laser-cycle dynamics of the recollision electron wave packet.
Scrinzi A, Ivanov MY, Kienberger R, et al., 2006, Attosecond physics, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 39, Pages: R1-R37, ISSN: 0953-4075
Experiments on the sub-femtosecond time scale performed in recent years and their theoretical background are reviewed in this article. We present the essentials of the generation of attosecond pulses, phase-stabilized few-cycle laser pulses, and applications to sub-femtosecond control of electronic motion and time-resolved spectroscopy of atoms and molecules. An outlook on emerging pulse-generation techniques and time-resolved imaging of electronic and molecular structure is included.
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