  The nucleus of 229Thorium presents a unique isomer state of very low energy
and long lifetime, current estimates are around 7.8 eV and seconds to hours
respectively. This nuclear transitions therefore is a promising candidate for a
novel type of frequency standard and several groups worldwide have set out to
investigate this system. Our aim is to construct a "solid state nuclear clock",
i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride
crystals transparent in vacuum ultraviolet range. As a first step towards an
accurate determination of the exact energy and lifetime of this isomer state we
perform low-resolution fluorescent spectroscopic measurements.
