Observation of resonance structures in 4d photoionization of Eu+

The relative photoion yield in the 4d photoionization of Eu+ has been measured with an energy resolution of E/ΔE≃820. The obtained spectrum shows that the 4d 'giant resonance' of Eu+ is not a single peak but consists of many resonances. The result is compared with a recent theoretical calculation and our previous result which has been measured with lower resolution. The calculation well reproduces the experimental result in the region of E≥140 eV, while some peaks are not corresponding in lower energy region.