Photodissociation of ThF$+$ and the eEDM

ThF$+$ has been chosen as the candidate for a third-generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF$+$ eEDM experiment, ThF$+$ has several advantages: (i) the eEDM-sensitive state (3$\Delta $1) is the ground state [1], which facilitates a long coherence time; (ii) and its effective electric field (35 GV/cm) is 50{\%} larger than that of HfF$+$ [2], which promises a direct increase of the eEDM sensitivity. However, molecular state detection is complicated by the molecular internal structure. Furthermore, current efficiency levels in the state preparation of ThF$+$ limits us to only a few hundred ThF$+$ ions within the trap for the eEDM experiment. Hence, we require a high-efficiency state readout method. One such method involves state-selective photodissociation of the ions, and counting the dissociated ions on a time-of-flight detector. However, the dissociating states of ThF$+$, which are required for the eEDM state readout, have not been found previously. Herein, we present the results of our spectroscopy of the ThF$+$ dissociating states, and our current progress in the state preparation of ThF$+$ for the eEDM experiment. [1] Gresh, Daniel N., et al. JMS 319 (2016): 1-9. [2] Skripnikov, L. V., and A. V. Titov. PRA 91.4 (2015): 042504.