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Optical and EUV spectroscopy of highly charged ions near the 4 f –5s level crossing


Bekker,  Hendrik
Division Prof. Dr. Thomas Pfeifer, MPI for Nuclear Physics, Max Planck Society;

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Bekker, H. (2016). Optical and EUV spectroscopy of highly charged ions near the 4 f –5s level crossing. PhD Thesis, Ruprecht-Karls-Universität, Heidelberg.

Cite as: https://hdl.handle.net/11858/00-001M-0000-002A-6CA5-5
In recent years, various highly charged ions (HCI) with optical transitions have been proposed for metrology and searches of a possible variation of the fine-structure constant α. Optical transitions in HCI are uncommon due to the scaling of energy levels with atomic number Z2. At the 4 f –5s level crossing, three configurations are nearly degenerate, and thus many optical transitions can exist. The complex many-electron couplings reduce the accuracy of current calculations. Moreover, experimental data to benchmark the predictions is lacking. Spectra in the optical and extreme-ultraviolet (EUV) range of several ion species near the 4 f –5s level crossing were measured at the Heidelberg electron beam ion trap. A collisionalradiative model was employed for the interpretation of the EUV data, resulting in the first identification of the long sought-after 5s–5p transitions in Pm-like Re14+, Os15+, Ir16+, and Pt17+. The characteristic line shapes of optical transitions in Ir17+ were studied, with the aim of identifying transitions with a high sensitivity to α-variation. Previously suggested candidates could be excluded and new candidates were proposed. This data provides a stringent benchmark for state-of-the-art precision atomic theory.