Internal conversion from excited electronic states of ${}^{229}\mathrm{T}h$ ions

The process of internal conversion from excited electronic states is investigated theoretically for the case of the vacuum-ultraviolet nuclear transition of ${}^{229}\mathrm{T}h$. Due to the very low transition energy, the ${}^{229}\mathrm{T}h$ 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.