Polarization mechanism for bremsstrahlung and radiative recombination in a plasma with heavy ions

The role of the polarization mechanism in bremsstrahlung and radiative recombination in a plasma with heavy ions is investigated. A study is made of a hot plasma with the electron temperature Te=0.5 keV, containing Fe, Mo, W, and U ions, a relatively cold plasma with a temperature of 0.1–10 eV, and a storage-ring plasma with relatively low-energy electrons. The spectral characteristics, as well as the total cross sections and rate constants for electron-ion recombination, are calculated with allowance for real ionization equilibrium in a plasma. The calculations are carried out using the quasiclassical approximation for electron scattering and the statistical model for the ions, which provides a universal description of the spectra of various chemical elements over a wide temperature range. It is shown that the polarization mechanism contributes to both the effective radiation intensity and the total radiative recombination rate. The temperature range is found where the polarization recombination of electrons in collisions with FeIII ions plays an important role, which indicates the collective behavior of the electron core of an iron ion in this temperature range. Taking into account polarization effects increases the calculated total continuum intensity. As a consequence, the effective plasma charge Zeff determined from this intensity without allowance for polarization effects turns out to be overestimated.