Progress Toward Measurement of the Electron's Electric Dipole Moment Using the PbF Molecule

The PbF molecule is particularly suited to a search for the electron's electric dipole moment ($e$-EDM.) In addition to its sensitivity to an $e$-EDM, its $^2\Pi_{1/2}$ ground state provides for a small magnetic moment. Furthermore, this small magnetic moment vanishes at a magic value of electric field. This vanishing point has an experimentally observable signature: When a beam of suitably aligned ground state PbF molecules is allowed to traverse a region of electric and magnetic fields, the polarization is conserved when the electric field matches this magic value. By measuring the (molecular-frame)magnitude of this magic electric field for the case that the electric field is parallel or antiparallel to the magnetic field, sensitivity to the $e$-EDM is achieved. Progress toward this measurement, including the development of a continuous molecular beam source of PbF, characterization of the electronic, rotational, and hyperfine structure of the molecule, the achievement of an ultra-sensitive continuous ionization detection scheme, and the construction of a Ramsey- resonance machine are briefly summarized.