Cascade effects on the polarization of He-like Fe1s2l−1s2x-ray line emission

Abstract

Abstract. We calculate X-ray line polarization degrees for cases with axial symmetry using a collisional-radiative magnetic-sublevel atomic kinetics model and the properties of multipole radiation fields. This approach is well-suited for problems where the alignment is determined by the competition between many atomic processes. We benchmark this method against polarization measurements performed at the Livermore electron beam ion trap, and we study the 3-to-2 cascade effects on the polarization of 2-to-1 lines in He-like Fe.

Opacity effects on the polarization of line emissions in astrophysical plasmas

“…where f are fractional (dimensionless) magnetic sublevel populations, N i is the total ion number density, and MI's are the relative multipole intensities for a given line of sight (usually at 90 • with respect to the quantization axis) (Hakel et al 2007). The polarization-dependent total line intensities I ||,⊥ satisfy the radiation transport equation,…”

“…They are characterized by a collection of quantum numbers, which include the total angular momentum J and its projection M along the quantization axis. To calculate the line emission characteristics we have used the collisional-radiative model for magnetic sublevels POLAR (Hakel et al, 2004(Hakel et al, , 2007 which we have augmented to account for opacity effects. POLAR is a two-step model in which the level populations are calculated first and are then postprocessed by a spectral model which extracts the line properties such as intensity and polarization degree.…”

Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments

“…In the past, we have separately modeled: (1) polarized line emissions in the optically thin approximation [25][26]; and (2) the opacity effects on unpolarized emission lines [27][28][29]. In this work, we combined elements of both efforts and arrived at a formalism that allows the postprocessing of magnetic-sublevel atomic kinetics calculations with a radiation-transport model adapted to describe the evolution of all four Stokes parameters needed to characterize polarized radiation.…”

Properties of Auger electrons following ionization of polarized atoms by polarized electrons

“…Recently Da Pieve et al [5] have commenced studying the angular correlation between a photoelectron and a subsequent Auger electron from atomic target by using single-particle approach avoiding density matrix formalism. For the calculation of polarized line emission, the method based on a collisional-radiative kinetic model of magnetic sublevel populations was recently used by Hakel et al [6]. Another method applied as an alternative approach with respect to the usual density matrix formalism was based on the methods developed in the atomic theory [7][8][9].…”

“…The ionized atom can 'remember' the direction of polarization of the incident electron or photon and the following Auger electron may have a nonisotropic angular distribution [2]. For the investigation of such processes, a number of methods have been developed [2][3][4][5][6][7]. Density matrix formalism [3] is the usual method for the investigation of polarization and angular distributions in two-step processes.…”