1,721,248 research outputs found
Igor Ivanov Speaking From the Podium at the Dayton Peace Accords
No full textRussian Deputy Foreign Minister Igor Ivanov speaks from behind the podium at the Dayton Peace Accords signing event, held at Wright-Patterson Air Force Base. European Union Ambassador Carl Bildt stands behind him.https://corescholar.libraries.wright.edu/special_ms458_photographs/1207/thumbnail.jp
Igor Ivanov Speaking From the Podium at the Dayton Peace Accords
No full textRussian Deputy Foreign Minister Igor Ivanov speaks from behind the podium at the Dayton Peace Accords signing event, held at Wright-Patterson Air Force Base. European Union Ambassador Carl Bildt stands behind him.https://corescholar.libraries.wright.edu/special_ms458_photographs/1208/thumbnail.jp
Igor Ivanov Speaking From the Podium at the Dayton Peace Accords
No full textRussian Deputy Foreign Minister Igor Ivanov speaks from behind the podium at the Dayton Peace Accords signing event, held at Wright-Patterson Air Force Base. European Union Ambassador Carl Bildt stands behind him.https://corescholar.libraries.wright.edu/special_ms458_photographs/1206/thumbnail.jp
Igor Ivanov Speaking From the Podium at the Dayton Peace Accords
No full textRussian Deputy Foreign Minister Igor Ivanov speaks from behind the podium at the Dayton Peace Accords signing event, held at Wright-Patterson Air Force Base. European Union Ambassador Carl Bildt stands behind him.https://corescholar.libraries.wright.edu/special_ms458_photographs/1209/thumbnail.jp
Correlation analysis of frustrated tunneling ionization
No full textWe visualize frustrated tunneling ionization (FTI) using the correlation function analysis outlined in our preceding works [I. Ivanov and K. T. Kim, J. Phys. B 55, 055001 (2022)0953-407510.1088/1361-6455/ac5813; Sci. Rep. 12, 19533 (2022)2045-232210.1038/s41598-022-24168-8]. We apply this technique to the hydrogen atom subjected to a strong laser field. Our analysis supports the basic premises of the theory of FTI and demonstrates its sensitive dependence on the laser pulse duration and carrier envelope phase. © 2023 American Physical Society.11Nsciescopu
Tracking quantum-cloud expansion in tunneling ionization
No full textWe study the formation and evolution of the electron wave packets in the process of strong-field ionization of various atomic targets. Our study is based on reformulating the problem in terms of conditional amplitudes, i.e., the amplitudes describing outcomes of measurements of different observables provided that the electron is found in the ionized state after the end of the pulse. By choosing the electron coordinate as such an observable, we are able to unambiguously define the notion of the ionized wave packets and study their formation and spread. We show that the evolution of the ionized wave packets obtained in this way closely follows the classical trajectories at the initial stages of evolution providing an ab initio quantum mechanical confirmation of the basic premises of the classical Monte Carlo calculations approach. At the later stages of evolution, the picture becomes more complicated due to the wave packets' spread and due to interference of wave packets originating from different field maxima. Our approach also allows us to obtain information about the coordinate and velocity electron distributions at the tunnel exit. © 2023 American Physical Society.11Nsciescopu
Strong-field ionization of argon: Electron momentum spectra and nondipole effects
No full text©2022 American Physical SocietyWe investigate the influence of relativistic nondipole effects on the photoelectron spectra of argon, particularly in the low-kinetic-energy region (0-1 eV). In our experiment, we use intense, linearly polarized 800-nm laser pulses to ionize Ar from a jet and we record photoelectron energy and momentum distributions using a reaction microscope. Our measurements show that nondipole effects can cause an energy-dependent asymmetry along the laser propagation direction in the photoelectron energy and momentum spectra. Model simulation based on the time-dependent Dirac equation can reproduce our measurement results. Moreover, the electron trajectory analysis based on the classical model reveals that the photoelectrons obtain a negative momentum shift in the laser propagation direction due to the interplay between the Lorentz-force-induced radiation pressure during its free propagation in the continuum and rescattering by the Coulomb potential of the parent ion when it is driven back by the laser field.11Nsciescopu
Interference patterns in ionization of Kramers–Henneberger atom
No full textWe combine IR pump and XUV probe laser pulses to visualize the Kramers–Henneberger (KH) state of the potassium atom. We demonstrate that ionization of such an atom exhibits some molecular-like features such as low order interference maxima in photoelectron momentum spectra. The locations of these maxima allow to estimate spatial dimensions of the KH atom and can be used for accurate calibration of high intensity laser fields. At the same time, we show that an analogy between the KH atom and a homo-nuclear diatomic molecule cannot be extended too far. In particular, higher order interference maxima are very difficult to observe in the case of the KH state. We attribute this to a particular structure of the KH potential which does not confine electron motion to a well-defined potential well unlike in real diatomic molecules
Attosecond angular streaking and tunnelling time in atomic hydrogen
No full textThe tunnelling of a particle through a potential barrier is a key feature of quantum mechanics that goes to the core of wave-particle duality. The phenomenon has no counterpart in classical physics, and there are no well constructed dynamical observables that could be used to determine 'tunnelling times'. The resulting debate(1-5) about whether a tunnelling quantum particle spends a finite and measurable time under a potential barrier was reignited in recent years by the advent of ultrafast lasers and attosecond metrology(6). Particularly important is the attosecond angular streaking ('attoclock') technique(7), which can time the release of electrons in strong-field ionization with a precision of a few attoseconds. Initial measurements(7-10) confirmed the prevailing view that tunnelling is instantaneous, but later studies(11,12) involving multi-electron atoms-which cannot be accurately modelled, complicating interpretation of the ionization dynamics-claimed evidence for finite tunnelling times. By contrast, the simplicity of the hydrogen atom enables precise experimental measurements and calculations(13-15) and makes it a convenient benchmark. Here we report attoclock and momentum-space imaging(16) experiments on atomic hydrogen and compare these results with accurate simulations based on the three-dimensional time-dependent Schrodinger equation and our experimental laser pulse parameters. We find excellent agreement between measured and simulated data, confirming the conclusions of an earlier theoretical study(17) of the attoclock technique in atomic hydrogen that presented a compelling argument for instantaneous tunnelling. In addition, we identify the Coulomb potential as the sole cause of the measured angle between the directions of electron emission and peak electric field: this angle had been attributed(11,12) to finite tunnelling times. We put an upper limit of 1.8 attoseconds on any tunnelling delay, in agreement with recent theoretical findings(18) and ruling out the interpretation of all commonly used 'tunnelling times'(19) as 'time spent by an electron under the potential barrier'(20) © The Author(s), under exclusive licence to Springer Nature Limited 201
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