2,557 research outputs found

    Semiclassical two-step model for ionization of hydrogen molecule by strong laser field

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    We extend the semiclassical two-step model for strong-field ionization that describes quantum interference and accounts for the Coulomb potential beyond the semiclassical perturbation theory to the hydrogen molecule. In the simplest case of the molecule oriented along the polarization direction of a linearly polarized laser field, we predict significant deviations of the two-dimensional photoelectron momentum distributions and the energy spectra from the case of atomic hydrogen. Specifically, for the hydrogen molecule the electron energy spectrum falls off slower with increasing energy, and the holographic interference fringes are more pronounced than for the hydrogen atom at the same parameters of the laser pulse.Comment: 9 pages, 6 figure

    Reconstruction of a single-active-electron potential from electron momentum distribution produced by strong-field ionization using optimization technique

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    We present a method for retrieving of single-active electron potential in an atom or molecule from a given momentum distribution of photoelectrons ionized by a strong laser field. In this method the potential varying within certain limits is found as the result of the optimization procedure aimed at reproducing the given momentum distribution. The optimization using numerical solution of the time-dependent Schrodinger equation for ionization of a model one-dimensional atom shows the good accuracy of the potential reconstruction method. This applies to different ways used for representing of the potential under reconstruction, including a parametrization and determination of the potential by specifying its values on a spatial grid.Comment: 18 pages, 6 figure

    Transfer learning, alternative approaches, and visualization of a convolutional neural network for retrieval of the internuclear distance in a molecule from photoelectron momentum distributions

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    We investigate the application of deep learning to the retrieval of the internuclear distance in the two-dimensional H2+_2^{+} molecule from the momentum distribution of photoelectrons produced by strong-field ionization. We study the effect of the carrier-envelope phase on the prediction of the internuclear distance with a convolutional neural network. We apply the transfer learning technique to make our convolutional neural network applicable to distributions obtained for parameters outside the ranges of the training data. The convolutional neural network is compared with alternative approaches to this problem, including the direct comparison of momentum distributions, support-vector machines, and decision trees. These alternative methods are found to possess very limited transferability. Finally, we use the occlusion-sensitivity technique to extract the features that allow a neural network to take its decisions.Comment: 28 pages, 7 figures, 1 tabl

    Semiclassical two-step model for strong-field ionization

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    We present a semiclassical two-step model for strong-field ionization that accounts for path interferences of tunnel-ionized electrons in the ionic potential beyond perturbation theory. Within the framework of a classical trajectory Monte-Carlo representation of the phase-space dynamics, the model employs the semiclassical approximation to the phase of the full quantum propagator in the exit channel. By comparison with the exact numerical solution of the time-dependent Schr\"odinger equation for strong-field ionization of hydrogen, we show that for suitable choices of the momentum distribution after the first tunneling step, the model yields good quantitative agreement with the full quantum simulation. The two-dimensional photoelectron momentum distributions, the energy spectra, and the angular distributions are found to be in good agreement with the corresponding quantum results. Specifically, the model quantitatively reproduces the fan-like interference patterns in the low-energy part of the two-dimensional momentum distributions as well as the modulations in the photoelectron angular distributions.Comment: 31 pages, 7 figure

    Study of the Forces Acting on the Animal in the Installation for Fixing with Veterinary Treatments

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    The study of the forces acting on the animal in the installation for fixing with veterinary treatments. The most time consuming processes in service animals are zootechnical and veterinary treatment of sheep. During the year, it is necessary to carry out more than ten such treatments of each animal, which requires a lot of labor. Almost all animal treatments such as feed to the operator’s workplace and their fixation in a convenient position for him requires significant physical effort of the operator. Therefore, today the technologies and technical means should be created to reduce labor costs for various treatments. The relevance of the problem is due to the lack of theoretical foundations and experimental data for the creation of technological equipment for fixing sheep in zootechnical and veterinary treatments. The purpose of the study is the theoretical and experimental justification of the installation for fixing sheep in zootechnical and veterinary treatments with the justification of the existing efforts on the animal, excluding injury. Developed installation and presented a scheme with two of the conveyor belts forming the grooved shape When designing the installation, the main focus was on the justification of structural elements and modes of operation from the viewpoint of eliminating the possibility of injury to the animal. The experimental studies have confirmed the correctness of the obtained analytical dependences. The obtained results will enable designers to create equipment for the fixation of sheep at the zootechnical and veterinary treatments, precluding injury to the animal and reducing labor costs

    Petroleum desalting by electrically pulverized rinsing water

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    A method of preparing petroleum and rinsing water emulsion using electric pulverization is described. The influence of various factors on the process of electric pulverization was studied in laboratory electropulverizing devices (EPD) with different lay out and configuration of electrodes. It is shown that by increasing electric field intensity, the size of water drops introduced into petroleum can be varied from a hundred to several micrometers with high degree of their monodispersion. It is ascertained that with an increase in electric conductivity the mean diameter of water drops reduces insignificantly. The emulsion dispersion does not depend on petroleum electric coductivity. With a decrease in interphase tension the mean size of drops in dispersed phase decreases. The possibility to improve petroleum desalting using EPD with required distribution of rinsing water drops over sizes is confirmed

    Momentum distributions of sequential ionization generated by an intense laser pulse

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    Journals published by the American Physical Society can be found at http://publish.aps.org/The relative yield and momentum distributions of all multiply charged atomic ions generated by a short (30 fs) intense (10(14)-5 x 10(18) W/cm(2)) laser pulse are investigated using a Monte Carlo simulation. We predict a substantial shift in the maximum (centroid) of the ion-momentum distribution along the laser polarization as a function of the absolute phase. This effect should be experimentally detectable with currently available laser systems even for relatively long pulses, such as 25-30 fs. In addition to the numerical results, we present semianalytical scaling for the position of the maximum
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