Parity Nonconservation in Atomic Thallium

Abstract

We present new measurements of parity conservation in the 293-nm transition in atomic $_{81}^{205}\mathrm{Tl}$. Linearly polarized 293-nm photons, polarization $\stackrel{^}{\ensuremath{\epsilon}}$, are absorbed by $6^{2}P_{\frac{1}{2}}$ atoms in crossed electric and magnetic fields. The transition probability for each Zeeman component contains a term proportional to $\stackrel{^}{\ensuremath{\epsilon}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}\stackrel{^}{\ensuremath{\epsilon}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ifmmode\times\else\texttimes\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ arising from interference between the Stark $E1$ amplitude $\ensuremath{\beta}E$ and the parity-nonconserving $E1$ amplitude ${\mathcal{E}}_{p}$. Our result, ${[\mathrm{Im}\frac{{\mathcal{E}}_{p}}{\ensuremath{\beta}}]}_{\mathrm{expt}}=\ensuremath{-}1.73\ifmmode\pm\else\textpm\fi{}0.33$ mV/cm, is compared with estimates based on the standard electroweak model.