No abstract

We report a measurement of parity non-conserving (PNC) optical rotation in the vicinity of the 1.279 µm magnetic dipole transition in atomic lead. We obtain a value for the conventional parameter, R = Im E1 PNC / M1 = (−9.80 ± 0.33) × 10 −8 , with limits on the nuclear spin-dependent contribution set by the anapole constant κ a = −2.0 (17.0). The experimental results, when combined with the relevant atomic calculations, lead to a value for the mass of the Z 0 boson or, alternatively, place a limit on physics beyond the standard model through the isospin-conserving parameter, S.

We give a theory of magneto-optic rotation and pseudorotation spectra for forbidden transitions. The case considered is that of a weak magnetic field at an arbitrary angle to the direction of light of low intensity passing through a dilate atomic vapour. The theory is applied to the 1279 nm M1 transition in atomic lead and the 1283 nm M1/E2 transition in atomic thallium. Experimental Voigt and Faraday effect data for lead measured in a sensitive optical polarimeter provide confirmation of the predicted profiles.