Progress towards parity nonconservation in atomic ytterbium

We have made measurements on the forbidden 6s2 1S 0 → 5d6s 3D1 transition in atomic ytterbium. These measurements are a significant step in the on-going effort to study atomic parity nonconservation utilizing this transition. This transition is expected to exhibit significantly larger parity-nonconserving effects than those studied in other atoms and is well suited for the study of both nuclear-spin-independent and nuclear-spin-dependent parity-nonconserving effects.; We have observed the magnetic-dipole amplitude for the transition using the technique of Stark interference. Ytterbium atoms were excited on the 6s 2 1S0 → 5d6s 3D 1 transition with resonant, linearly polarized light at 408 nm. The atoms were excited in the presence of electric and magnetic fields oriented to cause interference between the magnetic-dipole and Stark-induced electric-dipole transition amplitudes. The number of atoms excited was monitored through fluorescence at 556 nm resulting from the 6s6p 3P1 → 6s 2 1S0 branch of the decay. The direction of the fields was changed to separate out the contribution from the interference term. We find |⟨5d6s 3D1|mu|6s2 1S0⟩| = 1.33(6)Stat(6) beta x 10-4mu0, where the second error comes from the uncertainty in the vector transition polarizability, beta. This measurement also constitutes the first reported observation of magneto-electric Jones dichroism; a difference in absorption between light polarized at +/-45° relative to the direction of the collinear electric and magnetic fields.; We have also implemented a high-finesse optical power build-up cavity, an essential ingredient for the future parity-nonconservation experiment. The frequency of the 408-nm light was locked to the power-build up cavity and the resonant frequency of the cavity was scanned over the atomic resonance. Ytterbium atoms were excited within the cavity in the presence of a dc electric field and the spectral line shapes were observed through fluorescence at 556 nm. The spectral line was modeled using a density-matrix calculation that included the effects of ac-Stark shifts on the transition resulting from the intense light field inside the cavity. By comparing the calculation with the experiment we extracted a value for a combination of the scalar and tensor ac-Stark shifts of the 6s2 1S0 → 5d6s 3D1 transition resulting from light at 408 nm.