Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe <scp>xxv</scp>–<scp>xxi</scp> Ions

Abstract We report on comprehensive laboratory studies of the K-shell dielectronic recombination resonances of Fe xxv – xxi ions that prominently contribute to the hard X-ray spectrum of hot astrophysical plasmas. By scanning a monoenergetic electron beam to resonantly excite trapped Fe ions in an electron beam ion trap and achieving a high electron–ion collision energy resolution of ∼7 eV, we resolve their respective KL n satellites up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:mn>11</mml:mn> </mml:math> . By normalization to known radiative recombination cross sections, we also determine their excitation cross sections and that of the continuum with uncertainties below 15% and verify our results with an independent normalization based on previous measurements. Our experimental data excellently confirm the accuracy and suitability of distorted-wave calculations obtained with the Flexible Atomic Code for modeling astrophysical and fusion plasmas.