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Abstract:
Photoionization (PI) of multiply and highly charged ions was studied using an electron beam
ion trap and synchrotron radiation at the BESSY II electron storage ring. The versatile new
method introduced here extends the range of ions accessible for PI investigations beyond
current limitations by providing a dense target of ions in arbitrary, i.e. both low and high
charge states. Data on near-threshold PI of N3+ and Ar8+ ions, species of astrophysical and
fundamental interest, show high resolution and accuracy allowing various theoretical models
to be distinguished, and highlight shortcomings of available PI calculations. We compare our
experimental data with our new fully relativistic PI calculations within a multiconfiguration
Dirac–Fock approach and with other advanced calculations and find generally good
agreement; however, detailed examination reveals significant deviations, especially at the
threshold region of Ar8+.
