  The LIBELLE experiment performed at the experimental storage ring (ESR) at
the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, has
successfully determined the ground state hyperfine (HFS) splittings in
hydrogen-like ($^{209}\rm{Bi}^{82+}$) and lithium-like ($^{209}\rm{Bi}^{80+}$)
bismuth. The study of HFS transitions in highly charged ions enables precision
tests of QED in extreme electric and magnetic fields otherwise not attainable
in laboratory experiments. Besides the transition wavelengths the time resolved
detection of fluorescence photons following the excitation of the ions by a
pulsed laser system also allows to extract lifetimes of the upper HFS levels
and g-factors of the bound 1s and 2s electrons for both charge states. While
the lifetime of the upper HFS state in $^{209}\rm{Bi}^{82+}$ has already been
measured in earlier experiments, an experimental value for lifetime of this
state in $^{209}\rm{Bi}^{80+}$ is reported for the first time in this work.
