Magnetic and electric dipole moments of the H 3Δ1 state in ThO

The metastable H 3Δ1 state in the thorium monoxide (ThO) molecule is highly sensitive to the presence of a CP-violating permanent electric dipole moment of the electron (eEDM) [E. R. Meyer and J. L. Bohn, Phys. Rev. A 78, 010502 (2008)]. The magnetic dipole moment μH and the molecule-fixed electric dipole moment DH of this state are measured in preparation for a search for the eEDM. The small magnetic moment μH=8.5(5)x10-3 μB displays the predicted cancellation of spin and orbital contributions in a 3Δ1 paramagnetic molecular state, providing a significant advantage for the suppression of magnetic field noise and related systematic effects in the eEDM search. In addition, the induced electric dipole moment is shown to be fully saturated in very modest electric fields (<10 V/cm). This feature is favorable for the suppression of many other potential systematic errors in the ThO eEDM search experiment.