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Abstract

In this work photoionization of multiply and highly charged ions is studied using an electron beam ion trap and synchrotron radiation at the BESSY II electron storage ring. The new method introduced here extends the range of ions accessible for photoionization investigations beyond current limitations by providing a well controllable target of ions at about three orders of magnitude higher densities compared to ion beam targets. Data on N3+, Ar8,10,12+ and Fe12,14+ show excellent resolution and sensitivity. This enables to benchmark numerous theoretical methods for the calculation of photoionization cross section in the range of high charge states and ionisation potentials for the first time. Thus the identification of emission and absorption lines in astrophysical spectra can be improved significantly. In this regard, a special emphasis should be given to the results of Fe14+, where L-shell excitations could be measured up to the keV regime. A resolving power of E/delta E 6500 was achieved, allowing for the accurate determination of resonance energies and splittings on a 100 and 10 ppm level, respectively. Moreover, a very promising approach toward the determination of absolute cross section was demonstrated.