Spectroscopic Characterization of Thorium Monoxide for use in an Electron Electric Dipole Momement Measurement*

The ACME Collaboration is searching for the electron electric dipole moment (eEDM) in the metastable H $^3\Delta_1$ state of thorium monoxide (ThO) using a cryogenic molecular beam.\footnote{A.C.~Vutha \textit{et al.}, Phys. B 43, 074007 (2010)} The primary molecular beam source has been fully characterized and optimized.\footnote{N.R.~Hutzler \textit{et al.}, arXiv:1101.4217 (2011)} We report on advances in characterizing the spectroscopic properties of the ThO molecule. Transitions necessary for H state preparation and detection have been observed for the the first time, and the saturation parameters for these transitions have been measured. The electric polarizability of the H state and its small g-factor have been measured. The lifetime of a key excited state has been measured. We also report on preliminary results on state preparation and readout of coherent precession phases.