SEARCH FOR PARITY NONCONSERVING OPTICAL ROTATION IN ATOMIC SAMARIUM

We have searched for parity nonconserving (PNC) optical rotation in five optical transitions within the ${4f}^{6}{6s}^{2}$ ground configuration of atomic samarium using laser polarimetry. It had been suggested that these transitions might be favorable for studying electroweak effects because the upper levels have close-lying levels of opposite parity which might give rise to strong mixing by the PNC Hamiltonian ${H}_{\mathrm{PNC}}.$ In terms of the usual parameter $R[=\mathrm{Im}({\mathcal{E}}_{\mathrm{PNC}}/\mathcal{M})],$ we obtain (in units of ${10}^{\ensuremath{-}8}$) ${R}_{662}=2.1(1.8),$ ${R}_{628}=\ensuremath{-}7(16),$ ${R}_{611}=\ensuremath{-}6(8),$ ${R}_{569}=\ensuremath{-}17(30),$ and ${R}_{558}=\ensuremath{-}6(12),$ where the subscripts give the wavelengths of the transitions. The values of R are not significantly greater than those already reported for the heavy elements bismuth, lead, and thallium, and we conclude that the samarium transitions do not offer the prospect of a critical test of electroweak theory. Upper limits on the matrix elements of ${H}_{\mathrm{PNC}}$ between the upper levels of the transitions and their close-lying opposite-parity neighbors are derived from the results.