Parity nonconservation in bismuth atoms and neutral weak-interaction currents

Results are presented of measurements of the natural optical activity of atomic bismuth vapor in the region of the M1 transition /sup 4/S/sub 3/2/--/sup 2/D/sub 5/2/ at l = 648 nm. The measured value of the circular polarization P = -2R = -2 Im (A(E1)/(M1)) = (40.4 +- 5.4) x 10/sup -8/ agrees with the results of the calculations performed within the framework of the Weinberg-Salam method with sin/sup 2/q = 0.25.