Precise measurement of parity nonconserving optical rotation at 876 nm in atomic bismuth

We report the first precise measurements of parity nonconserving (PNC) optical rotation in atoms, carried out on the 876-nm M1 transition in bismuth. We obtain ${\mathit{R}}_{\mathit{i}}$=Im(E$1_{\mathrm{PNC}}^{\mathit{i}}$/M1)=(-10.12±0.20)×${10}^{\mathrm{-}8}$, where E$1_{\mathrm{PNC}}^{\mathit{i}}$ is the E1 amplitude mixed into the transition by the nuclear spin-independent PNC interaction. The result is in excellent agreement with the standard model of the electroweak interaction. The amplitude of nuclear spin-dependent PNC rotation is found to be less than 1.5×${10}^{\mathrm{-}2}$ of that due to the nuclear spin-independent interaction.