Precision spectroscopy of the3s−3pfine-structure doublet inMg+

Abstract

We apply a recently demonstrated method for precision spectroscopy on strong transitions in trapped ions to measure both fine-structure components of the $3s\text{−}3p$ transition in ${{}^{24}\text{M}\text{g}}^{+}$ and ${{}^{26}\text{M}\text{g}}^{+}$. We deduce absolute frequency reference data for transition frequencies, isotope shifts, and fine-structure splittings that in particular are useful for comparison with quasar absorption spectra, which test possible space-time variations of the fine-structure constant. The measurement accuracy improves previous literature values, when existing, by more than two orders of magnitude.