Microscopic nonlinear relativistic quantum theory of absorption of powerful x-ray radiation in plasma

Abstract

The microscopic quantum theory of plasma nonlinear interaction with the coherent shortwave electromagnetic radiation of arbitrary intensity is developed. The Liouville-von Neumann equation for the density matrix is solved analytically considering a wave field exactly and a scattering potential of plasma ions as a perturbation. With the help of this solution we calculate the nonlinear inverse-bremsstrahlung absorption rate for a grand canonical ensemble of electrons. The latter is studied in Maxwellian, as well as in degenerate quantum plasma for x-ray lasers at superhigh intensities and it is shown that one can achieve the efficient absorption coefficient in these cases.

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

“…Comparison of this intensity threshold with the analogous one for the plasma electrons shows the substantial difference I χ 0 =1 /I χ=1 ∼ 30 between the values of these thresholds (instead of the light speed here stands up the Fermi velocity -much less than the light speed in vacuum). Thus, for realization of multiphoton SB in BG one can expect ∼ 30 times smaller intensities than for SB in atoms [7], [8], [33,36,37]. In addition, the considered in the present paper pump wave photon energy range of interest lies in the terahertz or near infrared domain, where the high-power terahertz or near-infrared generators and frequency multipliers are of special interest.…”

“…More than twenty years single layer graphene (SG) [1,2] has attracted the giant interest for its unusual electronic transport and the characteristics of relativistic charge carriers behaving like massless chiral Dirac fermions [3][4][5][6][7][8][9][10][11][12][13][14]. Bilayer graphene (BG) are consisted of two graphene AB stacked single layers.…”

“…The χ 0 is the ratio of the amplitude of the momentum given by the wave field to momentum at the one-photon absorption. Hence the intensity of the wave expressed by the parameter χ 0 can be estimated as I χ 0 = χ 2 0 × 1.74 × 10 12 Wcm −2 ( ω/eV) 3 [8]. Multiphoton effects become essential at χ 0 ∼ 1, which for terahertz photons ω ∼ 0.01 eV corresponds to intensity I χ 0 = 1.74 × 10 6 Wcm −2 .…”

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

“…We have excluded the hole operators in Eqs. (17)- (20), since the contribution of electron-holes intermediate states will be negligible for considered EM radiation intensities and Fermi energies. Taking into account anticommutation rules (18), (19) and Eqs.…”

“…The χ 0 is the ratio of the amplitude of the momentum given by the wave field to momentum at the one-photon absorption. The intensity of the wave expressed by the parameter χ 0 can be estimated as I χ 0 = χ 2 0 × 1.74 × 10 12 Wcm −2 ( ω/eV) 3 [20]. Multiphoton effects become essential at χ 0 ∼ 1, which for terahertz photons ω ∼ 0.01 eV corresponds to intensity I χ 0 ≃ 10 6 Wcm −2 .…”