5 results
Search Results
Now showing 1 - 5 of 5
- ItemPhase- and intensity-resolved measurements of above threshold ionization by few-cycle pulses(Bristol : IOP Publ., 2018-06-11) Kübel, M.; Arbeiter, M.; Burger, C.; Kling, Nora G.; Pischke, T.; Moshammer, R.; Fennel, T.; Kling, M.F.; Bergues, B.We investigate the carrier-envelope phase (CEP) and intensity dependence of the longitudinal momentum distribution of photoelectrons resulting from above threshold ionization of argon by few-cycle laser pulses. The intensity of the pulses with a center wavelength of 750 nm is varied in a range between 0.7 × 1014 and . Our measurements reveal a prominent maximum in the CEP-dependent asymmetry at photoelectron energies of 2 U P (U P being the ponderomotive potential), that is persistent over the entire intensity range. Further local maxima are observed around 0.3 and 0.8 U P. The experimental results are in good agreement with theoretical results obtained by solving the three-dimensional time-dependent Schrödinger equation. We show that for few-cycle pulses, the amplitude of the CEP-dependent asymmetry provides a reliable measure for the peak intensity on target. Moreover, the measured asymmetry amplitude exhibits an intensity-dependent interference structure at low photoelectron energy, which could be used to benchmark model potentials for complex atoms.
- ItemAttosecond streaking metrology with isolated nanotargets(Bristol : IOP Publ., 2018-01-05) Liu, Q.; Seiffert, L.; Trabattoni, A.; Castrovilli, M.C.; Galli, M.; Rupp, P.; Frassetto, F.; Poletto, L.; Nisoli, M.; Rühl, E.; Krausz, F.; Fennel, T.; Zherebtsov, S.; Calegari, F.; Kling, M.F.The development of attosecond metrology has enabled time-resolved studies on atoms, molecules, and (nanostructured) solids. Despite a wealth of theoretical work, attosecond experiments on isolated nanotargets, such as nanoparticles, clusters, and droplets have been lacking. Only recently, attosecond streaking metrology could be extended to isolated silica nanospheres, enabling real-time measurements of the inelastic scattering time in dielectric materials. Here, we revisit these experiments and describe the single-shot analysis of velocity-map images, which permits to evaluate the recorded number of electrons. Modeling of the recorded electron histograms allows deriving the irradiated nanoparticle statistics. Theoretically, we analyze the influence of the nanoparticle size on the field-induced delay, which is one of the terms contributing to the measured streaking delay. The obtained new insight into attosecond streaking experiments on nanoparticles is expected to guide wider implementation of the approach on other types of nanoparticles, clusters, and droplets.
- ItemCarrier-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.
- ItemImaging of carrier-envelope phase effects in above-threshold ionization with intense few-cycle laser fields(College Park, MD : Institute of Physics Publishing, 2008) Kling, M.F.; Rauschenberger, J.; Verhoef, A.J.; Hasović, E.; Uphues, T.; Milošević, D.B.; Muller, H.G.; Vrakking, M.J.J.Sub-femtosecond control of the electron emission in above-threshold ionization of the rare gases Ar, Xe and Kr in intense few-cycle laser fields is reported with full angular resolution. Experimental data that were obtained with the velocity-map imaging technique are compared to simulations using the strong-field approximation (SFA) and full time-dependent Schrödinger equation (TDSE) calculations. We find a pronounced asymmetry in both the energy and angular distributions of the electron emission that critically depends on the carrier-envelope phase (CEP) of the laser field. The potential use of imaging techniques as a tool for single-shot detection of the CEP is discussed. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
- ItemAttosecond electron spectroscopy using a novel interferometric pump-probe technique(College Park, Md. : APS, 2010) Mauritsson, J.; Remetter, T.; Swoboda, M.; Klünder, K.; L'Huillier, A.; Schafer, K.J.; Ghafur, O.; Kelkensberg, F.; Siu, W.; Johnsson, P.; Vrakking, M.J.J.; Znakovskaya, I.; Uphues, T.; Zherebtsov, S.; Kling, M.F.; Lépine, F.; Benedetti, E.; Ferrari, F.; Sansone, G.; Nisoli, M.We present an interferometric pump-probe technique for the characterization of attosecond electron wave packets (WPs) that uses a free WP as a reference to measure a bound WP. We demonstrate our method by exciting helium atoms using an attosecond pulse (AP) with a bandwidth centered near the ionization threshold, thus creating both a bound and a free WP simultaneously. After a variable delay, the bound WP is ionized by a few-cycle infrared laser precisely synchronized to the original AP. By measuring the delay-dependent photoelectron spectrum we obtain an interferogram that contains both quantum beats as well as multipath interference. Analysis of the interferogram allows us to determine the bound WP components with a spectral resolution much better than the inverse of the AP duration. © 2010 The American Physical Society.