X-ray absorption via electron-ion bremsstrahlung in Maxwellian plasma at the exact consideration of Coulomb potential

Based on the results of exact consideration of electron-ion Coulomb interaction, by numerical simulations for ultimate absorption coefficient, we study the practically more interesting case of absorption of hard x-ray quanta of frequency when photon energy is of the order of plasma temperature, in high temperature plasma, within the high nuclear charges as well (at which the Born approximation is not applicable), constituting the temperature dependence of one-photon absorption coefficient. It is shown that one can achieve the efficient absorption coefficient in these cases.Comment: 5 pages, 4 figure

Third harmonic generation in gapped bilayer graphene

With the help of numerical simulations in microscopic nonlinear quantum theory of coherent electromagnetic radiation interaction with a gapped bilayer graphene, we find out the optimal values of pump wave intensity, graphene temperature, and energy gap induced by a constant electric field for practically significant third order harmonic coherent emission. The Liouville-von Neumann equation is treated numerically for the third harmonic generation in multiphoton excitation regime near the Dirac points of the Brillouin zone. We examine the rates of the third harmonic at the particle-hole annihilation in the field of a strong pump wave of linear polarization for practically real/optimal parameters of a considering system. The obtained results show that by choosing the optimal values of the main characteristic parameters, a gapped bilayer graphene can serve as an effective medium for generation of the third harmonic at room temperatures in the terahertz and far infrared domains.Comment: 7 figure

Nonlinear absorption of high-intensity shortwave radiation in plasma within relativistic quantum theory

On the base of the quantum kinetic equation for density matrix in plasma at the stimulated bremsstrahlung of electrons on ions, the nonlinear absorption rate for high-intensity shortwave radiation in plasma has been obtained within relativistic quantum theory. Both classical Maxwellian and degenerate quantum plasma are considered for x-ray lasers of high intensities. Essentially different dependences of nonlinear absorption rate on polarization of strong laser radiation is stated.Comment: 8 pages, 9 figure

Microscopic quantum theory of nonlinear absorption of strong electromagnetic radiation in doped graphene

Microscopic quantum theory of nonlinear stimulated scattering of 2D Dirac particles in doped graphene on Coulomb field of impurity ions at the presence of an external strong coherent electromagnetic radiation is developed. We consider high Fermi energies and low frequencies (actually terahertz radiation) to exclude the valence electrons excitations. The Liouville-von Neumann equation for the density matrix is solved analytically, taking into account the interaction of electrons with the scattering potential in the Born approximation. With the help of this solution, the nonlinear inverse-bremsstrahlung absorption rate for a grand canonical ensemble of 2D Dirac fermions is calculated. It is shown that one can achieve the efficient absorption coefficient by this mechanism.Comment: 11 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:1703.0685

High-order harmonic generation in gapped bilayer graphene

Microscopic nonlinear quantum theory of interaction of coherent electromagnetic radiation with gapped bilayer graphene is developed. The Liouville-von Neumann equation for the density matrix is solved numerically at the multiphoton excitation regime. The developed theory of interaction of charged carriers with strong driving wave field is valid near the Dirac points of the Brillouin zone. We consider the harmonic generation process in the nonadiabatic regime of interaction when the Keldysh parameter is of the order of unity. On the basis of numerical solutions, we examine the rates of odd and even high-harmonics at the particle-hole annihilation in the field of a strong pump wave of arbitrary polarization. Obtained results show that the gapped bilayer graphene can serve as an effective medium for generation of even and odd high harmonics in the THz and far infrared domains of frequencies.Comment: 15 pages, 9 figure

Induced nonlinear cross sections of conductive electrons scattering on the charged impurities in doped graphene

Relativistic quantum theory of induced scattering of 2D Dirac particles by electrostatic field of impurity ion (in the Born approximation) in the doped graphene at the presence of an external electromagnetic radiation field (actually terahertz radiation, to exclude the valence electrons excitations at high Fermi energies) has been developed. It is shown that the strong coupling of massless quasiparticles in the quantum nanostructures to a strong electromagnetic radiation field leads to the strongly nonlinear response of graphene, which opens diverse ways for manipulating the electronic transport properties of conductive electrons by coherent radiation fields.Comment: 8 pages, 7 figure

Microscopic nonlinear quantum theory of absorption of coherent electromagnetic radiation in doped bilayer graphene

The microscopic quantum theory of nonlinear stimulated scattering of chiral particles in doped $AB$ stacked bilayer graphene on Coulomb field of charged impurities in the presence of strong coherent electromagnetic radiation is presented. The Liouville-von Neumann equation for the density matrix is solved analytically. Here the interaction of electrons with the scattering potential is taken into account as a perturbation. The absorption rate of nonlinear inverse-bremsstrahlung for a grand canonical ensemble of fermionic chiral particles is calculated using the obtained solution. The analysis of the obtained rate shows that in the terahertz and near-infrared range of frequencies there is significant absorption of incident radiation via multiphoton stimulated bremsstrahlung mechanism.Comment: 13 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1907.04692 and arXiv:1710.0368

The Dependence of the Age Parameter from EAS Size and Zenith Angle of Incidence

The quality of the MAKET-ANI detector installation in view of the uniformity of the registration efficiency is demonstrated. Based on a data sample collected by the MAKET-ANI array in the period of June 1997 - March 1999, the dependencies of the age parameter on the zenith angle and the EAS size (10^5-10^7) are studied. The variation of the age parameter with the shower size can be approximately related to the elongation rate.Comment: 6 pages, to appear in the ANI99 workshop proceedings, FZKA report Forschungszentrum Karlsruhe, ed. by A.Chilingarian, A.Haungs, H.Rebel and Kh.N.Sanosya

Determination of the EAS Attenuation Length from Data of the ANI Experiment

Using the EAS size spectra measured with the MAKET ANI array on Mt. Aragats, Armenia (3200m a.s.l.) in the range of the shower size 10^5 - 10^7 for different angles-of-incidence, the EAS attenuation length has been determined applying different analysis methods. The analysis is based on a data sample of 2.5*10^6 events collected in the period of June, 97 - April, 99. The results are compared with results deduced from data of the EAS TOP and KASCADE experiments.Comment: 9 pages, to appear in the ANI99 workshop proceedings, FZKA report Forschungszentrum Karlsruhe, ed. by A.Chilingarian, A.Haungs, H.Rebel and Kh.N.Sanosya

Multiphoton cross sections of conductive electrons stimulated bremsstrahlung in doped bilayer graphene

The quantum theory of multiphoton stimulated bremsstrahlung of charged carriers on an arbitrary electrostatic potential of impurity ion in doped bilayer graphene at the presence of coherent electromagnetic radiation is developed. A terahertz wave field is considered exactly, while the electrostatic potential of doped ions as a perturbation. The essentially nonlinear response of bilayer graphene to a pump wave and significant differences from the case of a single layer graphene are shown, which can be associated to nonlinear parabolic dispersion. The latter opens new way to manipulate with the electronic transport properties of conductive electrons of bilayer graphene by coherent radiation field of terahertz or near-infrared frequencies.Comment: 15 pages, 7 figures. arXiv admin note: text overlap with arXiv:1703.06854, arXiv:1710.0368