Progress Towards an Electron EDM Search Using Trapped Molecular Ions

A sample of trapped molecular ions can provide large effective electric fields and long electron spin coherence times in the search for a permanent electron electric dipole moment (EDM). We plan to use the $^3\Delta_1$ state of trapped HfF$^+$ in this search. The $^3\Delta_1$ state should yield effective internal fields of $\sim$10 V/cm and should be easily polarized in $\sim$1 V/cm electric fields due to the small $\Omega$-doublet splitting. Confinement of the ions in a linear Paul trap allows for long electron spin coherence times and thus increased sensitivity. We will report on preliminary HfF$^+$ spectroscopy and other experimental progress.