A search for parity violation in atoms

An experimental measurement of parity non-conserving (PNC) optical rotation is described in the frequency region of the J=3/2 to J'=5/2 magnetic dipole (Ml) absorption line (lambda648 nm) within the ground configuration 6p3 of atomic bismuth Bi I. PNC effects in atoms are predicted by the recent Weinberg-Salam unified field theory of the weak and electromagnetic interactions. The apparatus and method are described. The result R = (-10.43 +- 1.56) 10-8 was obtained where R = Im(El/Ml) is the ratio of the PNC El reduced matrix element to the parity conserving Ml reduced matrix element. The quoted error is one standard deviation. The value for R is to be compared with (a) two recent theoretical estimates R = -14 10-8 and R = 19 10-8 (both using the Weinberg-Salam theory with sin2 thetasub(W) = 0.25 but different techniques for the atomic calculation), and (b) another experimental measurement, R = (-20.2 +- 2.7) 10-8, by workers in Novosibirsk. (author)