  We report on the observation of time-resolved quantum beats in the helium
fluorescence from the transition 1s3p -> 1s2s, where the initial state is
excited by XUV free-electron laser radiation. The quantum beats originate from
the Zeeman splitting of the magnetic substates due to an external magnetic
field. We perform a systematic study of this effect and discuss the
possibilities of studying this phenomenon in the XUV and x-ray regime.
