Strong higher-order resonant contributions to x-ray line polarization in   hot plasmas
  We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work. 
Chintan Shah (1 and 2), Pedro Amaro (1), Rene Steinbr\"ugge (2),   Christian Beilmann (1 and 2), Sven Bernitt (2 and 3), Ste...
physics.atom-ph astro-ph.HE astro-ph.IM physics.plasm-ph