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Abstract

Contributions of trielectronic processes to resonant recombination of highly charged ions as well as the time reversed process of recombination, the resonant photoionization, were experimentally investigated with high resolution. For this hitherto mostly ignored excitation channels of a higher order with respect to dielectronic recombination (DR), unexpected high resonance strength values were found that can considerably influence the state of astrophysical or earthbound plasmas. Systematic studies of trielectronic recombination (TR) interacting between two principal shells in argon and iron – two elements of astrophysical relevance – allowed for the development of scaling laws in dependence of Z. Following them, the importance of TR for low-Z substantial increases, so TR strength can dominate over the respective first-order process (DR). The physical model of these processes was completed by investigations of the time reversed process, namely the photoionization of sodium-like iron. The fist simultaneous detection of the radiative relaxation of these photoexcited states by soft X rays lead to the determination of absolute resonance energies of an important group of transitions that had not been resolved in astrophysical spectroscopy. The comparison with our own configuration interaction-calculations enabled for a detailed analysis of influences by electron correlation and configuration mixing to both dynamical processes and demonstrated the unexpectedly strong influence of the Breitinteraction in ions of medium nuclear charge.