Polarization of hard X-ray dielectronic satellite lines from Na-like W ions

Abstract

One of the important signatures of non-thermal high-atomic-number multiply ionized plasmas is polarization of hard x-ray line emission. Atomic processes in laboratory and astrophysical plasmas with anisotropic electron distribution that can lead to such polarization include dielectronic recombination. All previous research on x-ray line polarization of dielectronic satellite lines was mostly focused on K-shell radiation. Here we present one of the first studies of polarization of L-shell dielectronic satellite lines using the hard x-ray spectra of Na-like W produced by dielectronic recombination. Polarization of dielectronic satellites is calculated using two approaches: density matrix formalism and the FAC code. The most intense dielectronic satellite lines of Na-like W appeared to be positively polarized with the maximum degree of polarization between 0.4545 and 0.6. Polarization-dependent dielectronic satellite spectra of Na-like W are calculated with a gaussian electron distribution function centered at the beam energies from 2400 eV to 4100 eV. Such spectra cover the spectral range from 1.19 Å to 1.38 Å with each spectrum including two traces of line intensities associated with the parallel polarization and perpendicular polarization state. The polarization-dependent spectra were found to be strongly dependent on the energy of the electron beam which can be used for the development of x-ray plasma polarization spectroscopy to study non-thermal multiply ionized W plasmas. Radiative and polarization properties of W radiation studied in this paper are important for fusion research.