Polarization-dependent spectra of x-ray dielectronic satellite lines of Be-like Fe

We have studied the polarization properties of dielectronic satellite lines in Be-like Fe ions excited through resonant electron capture by an electron beam. Using the photon density-matrix formalism, we have calculated the degree of polarization and polarization-dependent spectra of dielectronic satellite lines, i.e., the spectral intensity distribution of lines associated with a given polarization state. Theoretical results have been compared with experiments performed at the Lawrence Livermore National Laboratory electron-beam ion trap where dielectronic satellite line emission from Fe ions produced at different energies of the electron beam was simultaneously recorded with two crystal spectrometers. These spectrometers had different polarization sensitivities. The experimental spectra recorded by the two spectrometers are reproduced by the theory. This ability to model the polarization dependence of x-ray line spectra is important for the diagnosis of electron beams in plasmas.