Euv beam-foil observations of cu- through ge-like ions of iodine

The spectra and structure of multiply charged ions with an open n=4 shell have been studied for many years. For Cu-like and Zn-like ions, the data on the fundamental transitions obtained with laser-produced plasmas or an electron beam ion trap [1] cover quite a number of elements and reach up to uranium (Z=92). For ions with additional electrons in the valence shell, the data and corresponding calculations are much sparser. Also, the calculations tend to be the poorer the more electrons are added [2]. In the middle of the sequence of natural elements, classical light sources have reached their limit, and relativity and QED effects are not yet so large that they would arouse theoretical interest on their own. In short, the reasonably good coverage of the atomic spectra of multiply charged ions reaches only up to about Z=28 (Ni). The resonance and intercombination transitions in Cuand Zn-like ions are known or their trend established for the whole isoelectronic sequence. The lowest-energy ground state transitions in Ga-like ions are reasonably well known only up to about Mo (Z=42) and have been seen, for example, in beamfoil spectra up to Ag (Z=47) [3] (notwithstanding some observations at much higher Z in an EBIT).