arXiv subjects

E. Raicher

Publications and source records attributed to E. Raicher.

5 recordsLinked to original sources

arXiv2025

Nonresonant quantum dynamics of a relativistic electron in counterpropagating laser beams

The quantum dynamics of an ultrarelativistic electron in strong counterpropagating laser beams is investigated. In contrast to the stimulated Compton scattering regime, we consider the case when in the electron rest frame the frequency of the counterpropagating wave greatly exceeds that of the copropagating one. Taking advantage of the corresponding approximation recently developed by the authors for treating the classical dynamics in this setup, we solve the Klein-Gordon and Dirac equations in the quasiclassical approximation in the Wentzel-Kramers-Brillouin (WKB) framework. The obtained wave function for the Dirac equation shows entanglement between the kinetic momentum and spin of the electron, while the spin-averaged momentum coincides with the classical counterpart as expected. The derived wave functions will enable the calculation of the probabilities of nonlinear QED processes in this counterpropagating fields configuration.

hep-ph↗

arXiv2022

High-brilliance ultra-narrow-band x-rays via electron radiation in colliding laser pulses

A setup of a unique x-ray source is put forward employing a relativistic electron beam interacting with two counter-propagating laser pulses in the nonlinear few-photon regime. In contrast to Compton scattering sources, the envisaged x-ray source exhibits an extremely narrow relative bandwidth of the order of $10^{-4}$, comparable with an x-ray free-electron laser (XFEL). The brilliance of the x-rays can be an order of magnitude higher than that of a state-of-the-art Compton source. By tuning the laser intensities and the electron energy, one can realize either a single peak or a comb-like x-ray source of around keV energy. The laser intensity and the electron energy in the suggested setup are rather moderate, rendering this scheme compact and table-top size, as opposed to XFEL and synchrotron infrastructures.

physics.acc-ph↗

arXiv2021

Ultrarelativistic electrons in counterpropagating laser beams

The dynamics and radiation of ultrarelativistic electrons in strong counterpropagating laser beams are investigated. Assuming that the particle energy is the dominant scale in the problem, an approximate solution of classical equations of motion is derived and the characteristic features of the motion are examined. A specific regime is found with comparable strong field quantum parameters of the beams, when the electron trajectory exhibits ultrashort spike-like features, which bears great significance to the corresponding radiation properties. An analytical expression for the spectral distribution of spontaneous radiation is derived in the framework of the Baier-Katkov semiclassical approximation based on the classical trajectory. All the analytical results are further validated by exact numerical calculations. We consider a non-resonant regime of interaction, when the laser frequencies in the electron rest frame are far from each other, avoiding stimulated emission. Special attention is devoted to settings when the description of radiation via the local constant field approximation fails and to corresponding spectral features. Periodic and non-periodic regimes are considered, when lab frequencies of the laser waves are always commensurate. The sensitivity of spectra with respect to the electron beam spread, focusing and finite duration of the laser beams is explored.

physics.plasm-ph↗

arXiv2020

New class of violation of local constant field approximation in intense crossed laser pulse scenarios

It is commonly assumed that in ultrastrong laser fields, when the strong field parameter of the laser field $ξ$ is larger than one, the electron radiation is well described by the local constant field approximation (LCFA). We discuss the failure of this conjecture, considering radiation of an ultrarelativistic electron interacting with strong counterpropagating laser waves. A deviation from LCFA, in particular in the high-frequency domain, is shown to occur even at $ξ\gg 1$ because of the appearance of an additional small time scale in the trajectory. Moreover, we identify a new class of LCFA violation, when the radiation formation length becomes smaller than the one via LCFA. It is characterized by a broad and smooth spectrum rather than an harmonic structure. A similar phenomenon is also demonstrated in the scenario of an electron colliding with an ultrashort laser pulse. The relevance to laser-plasma kinetic simulations is discussed.

physics.plasm-ph↗

arXiv2018

Semi-classical limitations for photon emission in strong external fields

The semi-classical heuristic emission formula of Baier-Katkov [Sov. Phys. JETP \textbf{26}, 854 (1968)] is well-known to describe radiation of an ultrarelativistic electron in strong external fields employing the electron's classical trajectory. To find the limitations of the Baier-Katkov approach, we investigate electron radiation in a strong rotating electric field quantum mechanically using the Wentzel-Kramers-Brillouin approximation. Except for an ultrarelativistic velocity, it is shown that an additional condition is required in order to recover the widely used semi-classical result. A violation of this condition leads to two consequences. First, it gives rise to qualitative discrepancy in harmonic spectra between the two approaches. Second, the quantum harmonic spectra are determined not only by the classical trajectory but also by the dispersion relation of the effective photons of the external field.

hep-ph↗