Optical spectroscopy of highly charged ruthenium ions with astrophysical interest

Spectroscopic investigations into the abundances of trans-iron elements in stars yield valuable information about stellar evolution. In order to interpret the emission spectrum of these stars, spectral data of trans-iron elements is required. Ruthenium (Z=44) is particularly interesting as it has a similar atomic structure to that of technetium (Z=43), the lightest unstable element. The half-life of technetium is short compared to the life time of a star, allowing a time dependent insight into stellar evolution. In this work, highly charged ruthenium ions were produced and investigated in the Heidelberg electron beam ion trap at the Max Planck Institute of Nuclear Physics in Heidelberg. The uorescence light emitted by the excited ions was recorded using a Czerny-Turner monochromator. The 53 measured optical lines of the charge states Ru⁹⁺ to Ru¹⁸⁺ were compared to calculations from atomic theory, leading to tentative identifications of 30 transitions