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Start date: 2010 × search.filters.applied.f.series: New Journal of Physics 14 (2012) × WGL Institute: MBI ×

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Now showing 1 - 4 of 4
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    Interference structure of above-threshold ionization versus above-threshold detachment
    (Bristol : IOP, 2012) Korneev, Ph.A.; Popruzhenko, S.V.; Goreslavski, S.P.; Becker, W.; Paulus, G.G.; Fetić, B.; Milošević, D.B.
    Laser-induced electron detachment or ionization of atoms and negative ions is considered. In the context of the saddle-point evaluation of the strong-field approximation (SFA), the velocity maps of the direct electrons (those that do not undergo rescattering) exhibit a characteristic structure due to the constructive and destructive interference of electrons liberated from their parent atoms/ions within certain windows of time. This structure is defined by the above-threshold ionization rings at fixed electron energy and by two sets of curves in momentum space on which destructive interference occurs. The spectra obtained with the SFA are compared with those obtained by numerical solution of the time-dependent Schrödinger equation. For detachment, the agreement is excellent. For ionization, the effect of the Coulomb field is most pronounced for electrons emitted in a direction close to laser polarization, while for nearperpendicular emission the qualitative appearance of the spectrum is unaffected.
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    Attosecond streaking in a nano-plasmonic field
    (Bristol : IOP, 2012) Kelkensberg, F.; Koenderink, A.F.; Vrakking, M.J.J.
    A theoretical study of the application of attosecond streaking spectroscopy to time-resolved studies of the plasmonic fields surrounding isolated, resonantly excited spherical nanoparticles is presented. A classification of the different regimes in attosecond streaking is proposed and identified in our results that are derived from Mie calculations of plasmon fields, coupled to classical electron trajectory simulations. It is shown that in an attosecond streaking experiment, the electrons are almost exclusively sensitive to the component of the field parallel to the direction in which they are detected. This allows one to probe the different components of the field individually by resolving the angle of emission of the electrons. Finally, simulations based on fields calculated by finite-difference time-domain (FDTD) are compared with the results obtained using Mie fields. The two are found to be in good agreement with each other, supporting the notion that FDTD methods can be used to reliably investigate non-spherical structures.
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    Nanoplasmonic electron acceleration in silver clusters studied by angular-resolved electron spectroscopy
    (Bristol : IOP, 2012) Passig, J.; Irsig, R.; Truong, N.X.; Fennel, T.; Tiggesbäumker, J.; Meiwes-Broer, K.H.
    The nanoplasmonic field enhancement effects in the energetic electron emission from few-nm-sized silver clusters exposed to intense femtosecond dual pulses are investigated by high-resolution double differential electron spectroscopy. For moderate laser intensities of 10 14Wcm -2, the delaydependent and angular-resolved electron spectra show laser-aligned emission of electrons up to keV kinetic energies, exceeding the ponderomotive potential by two orders of magnitude. The importance of the nanoplasmonic field enhancement due to resonant Mie-plasmon excitation observed for optimal pulse delays is investigated by a direct comparison with molecular dynamics results. The excellent agreement of the key signatures in the delay-dependent and angular-resolved spectra with simulation results allows for a quantitative analysis of the laser and plasmonic contributions to the acceleration process. The extracted field enhancement at resonance verifies the dominance of surfaceplasmon-assisted re-scattering.
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    Carrier-envelope phase-tagged imaging of the controlled electron acceleration from SiO 2 nanospheres in intense few-cycle laser fields
    (Bristol : IOP, 2012) Zherebtsov, S.; Süßmann, F.; Peltz, C.; Plenge, J.; Betsch, K.J.; Znakovskaya, I.; Alnaser, A.S.; Johnson, N.G.; Kübel, M.; Horn, A.; Mondes, V.; Graf, C.; Trushin, S.A.; Azzeer, A.; Vrakking, M.J.J.; Paulus, G.G.; Krausz, F.; Rühl, E.; Fennel, T.; Kling, M.F.
    Waveform-controlled light fields offer the possibility of manipulating ultrafast electronic processes on sub-cycle timescales. The optical lightwave control of the collective electron motion in nanostructured materials is key to the design of electronic devices operating at up to petahertz frequencies. We have studied the directional control of the electron emission from 95 nm diameter SiO 2 nanoparticles in few-cycle laser fields with a well-defined waveform. Projections of the three-dimensional (3D) electron momentum distributions were obtained via single-shot velocity-map imaging (VMI), where phase tagging allowed retrieving the laser waveform for each laser shot. The application of this technique allowed us to efficiently suppress background contributions in the data and to obtain very accurate information on the amplitude and phase of the waveform-dependent electron emission. The experimental data that are obtained for 4 fs pulses centered at 720 nm at different intensities in the range (1-4)×10 13Wcm -2 are compared to quasi-classical mean-field Monte-Carlo simulations. The model calculations identify electron backscattering from the nanoparticle surface in highly dynamical localized fields as the main process responsible for the energetic electron emission from the nanoparticles. The local field sensitivity of the electron emission observed in our studies can serve as a foundation for future research on propagation effects for larger particles and field-induced material changes at higher intensities.