PRECISE TEST OF ELECTROWEAK THEORY FROM A NEW MEASUREMENT OF PARITY NONCONSERVATION IN ATOMIC THALLIUM

We report a new measurement of parity nonconserving (PNC) optical rotation near the 1.28 μm, 6P1/2→6P3/2 magnetic dipole transition in thallium. We find the ratio of the PNC E1 amplitude to the M1 amplitude to be R=(-14.68±0.17)×10-8, which within the present uncertainty of atomic theory yields the thallium weak charge Qw(T205l)=-114.2±3.8 and the electroweak parameter S=-2.2±3.0. Separate measurements on the F=1 and F=0 ground-state hyperfine components of the transition yield R1-R0=(0.15±0.20)×10-8, which limits the size of nuclear spin-dependent PNC in Tl. © 1995 The American Physical Society.