Absolute radiative and Auger transition rates of K-shell excited few-electron iron ions

The iron K alpha lines are among the most prominent features in the x-ray spectra of many celestial sources. However, transition rates used to model these spectra were only known by theoretical calculations. Here we present an absolute measurement, of iron K-shell transition rates for Li-like to C-like iron ions. These ions were created with an electron beam ion trap and excited with x rays from the PETRA III synchrotron source. Measuring x-ray fluorescence and Auger decay simultaneously allows to determine absolute decay rates independent of most experimental parameters.