We are pursuing an experiment to measure the electric dipole moment of the electron using the molecule PbO. This measurement requires the ability to prepare quantum states with orientation of the molecular axis and, simultaneously, alignment of the e
lectron spin perpendicular to this axis. It also requires efficient detection of the evolution of the spin alignment direction within such a state. We describe a series of experiments that have achieved these goals, and the features and limitations of the techniques. We also discuss possible new approaches for improved efficiency in this and similar systems.
We propose new experiments with high sensitivity to a possible spatial or temporal variation of the electron-to-proton mass ratio $mu equiv m_e/m_p$. We consider a nearly-degenerate pair of molecular vibrational levels, where each state is associated
with a different electronic potential. The change in the splitting between such levels, with respect to a change in $mu$, can be large both on an absolute scale and relative to the splitting. We demonstrate the existence of such pairs of levels in Cs$_2$. The narrow spectral lines achievable with ultracold Cs$_2$ in these long-lived levels make this system promising for future searches for small variations in $mu$.
Nuclear spin-dependent parity violation arises from weak interactions between electrons and nucleons, and from nuclear anapole moments. We outline a method to measure such effects, using a Stark-interference technique to determine the mixing between
opposite-parity rotational/hyperfine levels of ground-state molecules. The technique is applicable to nuclei over a wide range of atomic number, in diatomic species that are theoretically tractable for interpretation. This should provide data on anapole moments of many nuclei, and on previously unmeasured neutral weak couplings.
