Sarah Bickman

We have proposed and begun implementing an experiment to look for an electric dipole moment (EDM) of the electron, d e, using the metastable a(1) 3Sigma + state of the PbO molecule. A non-zero measurement of d e within the next few orders of magnitude beyond the current limit of ∣de∣ < 1.6 x 10-27 e-cm [1] would be clear evidence for physics beyond the standard model. We have designed and built a stable apparatus for the measurement of de using PbO* in a heated vapor cell. Using this apparatus, the O doublet splitting in the a(1) J=1 state was measured to be 11.214(5) MHz. Without an applied electric field, the difference in g-factors between the O doublet states was found to be deltag=-31(9) x 10-4. Measurements of the Stark shift were found to be consistent with previous measurements [2]. The counting rate has been optimized and agrees with models. Three different types of detectors with associated low-noise preamplifiers were built and tested. To improve the sensitivity, an alternate detection scheme using reexcitation to the C’ state was explored and ultimately rejected in the form proposed here. In the first generation experiment, with the current fluorescence detection along the a(1)→X transition, the expected sensitivity to an electron EDM is deltad e ≈10-25 e cm/ day. Two proposals for second generation experiments are considered.