  The process of internal conversion from excited electronic states is
investigated theoretically for the case of the vacuum-ultraviolet nuclear
transition of $^{229}{\mathrm Th}$. Due to the very low transition energy, the
$^{229}{\mathrm Th}$ nucleus offers the unique possibility to open the
otherwise forbidden internal conversion nuclear decay channel for thorium ions
via optical laser excitation of the electronic shell. We show that this feature
can be exploited to investigate the isomeric state properties via observation
of internal conversion from excited electronic configurations of ${\mathrm
Th}^+$ and ${\mathrm Th}^{2+}$ ions. A possible experimental realization of the
proposed scenario at the nuclear laser spectroscopy facility IGISOL in
Jyv\"askyl\"a, Finland is discussed.
