Abstract
The Coulomb focusing effect on the electron–atom bremsstrahlung spectrum is investigated in nonthermal Lorentzian plasmas. The universal expression of the cross section of nonrelativistic electron–atom bremsstrahlung process is obtained by the solution of the Thomas-Fermi equation with the effective atomic charge. The effective Coulomb focusing for the electron–atom bremsstrahlung cross section near the threshold domain is also investigated by adopting the modified Elwert-Sommerfeld factor with the mean effective charge for the bremsstrahlung process. In addition, the bremsstrahlung emission rates are obtained by considering encounters between nonthermal electrons and atoms such as Fe and W atoms. We found that the bremsstrahlung emission rates for nonthermal electron–atoms are lower than those for thermal plasmas. Various nonthermal effects on the bremsstrahlung emission rates in Lorentzian plasmas are also discussed.
Highlights
The bremsstrahlung processes [1,2,3,4,5,6,7,8,9,10,11,12] in thermal and nonthermal plasmas have received considerable attention in astrophysics and plasma physics since the continuum X-ray spectra due to the electron–nucleus and electron–atom bremsstrahlung processes have long been used for plasma diagnostics in various weakly coupled astrophysical plasmas
It is obvious that the Coulomb focusing factor for the electron-ion bremsstrahlung process is not the same with the electron–atom bremsstrahlung process because the effective charge of the bound atomic electrons is different from the total charge of the nucleus
It is expected that Equation (10) is the universal expression of the mean effective charge Ze f f for the bremsstrahlung and collision processes with many electron atoms since the effective charge is obtained by the Thomas-Fermi solution and the maximum momentum transfer is given by the main contribution region for the binary-encounter
Summary
The bremsstrahlung processes [1,2,3,4,5,6,7,8,9,10,11,12] in thermal and nonthermal plasmas have received considerable attention in astrophysics and plasma physics since the continuum X-ray spectra due to the electron–nucleus and electron–atom bremsstrahlung processes have long been used for plasma diagnostics in various weakly coupled astrophysical plasmas. The influence of atomic screening on the electron–atom bremsstrahlung cross section can be studied with the Thomas-Fermi statistical model [16] for many-electron atoms. The influence of Coulomb focusing on the electron–atom bremsstrahlung cross section and the radiation spectrum has not been investigated. We are motivated to study the bremsstrahlung process for electron–atom collision under the influence of atomic screening and Coulomb focusing correction in nonthermal plasmas. We derive the bremsstrahlung cross section for the electron–atom system by employing the Thomas-Fermi method with the effective charge of the atom. Elwert-Sommerfeld factor with the mean effective charge for the electron–atom interaction based on the Thomas-Fermi solution.
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