温伯格萨拉姆的弱相互作用理论预示原子中存在着宇称不守恒(PNC)效应,而且在重原子中,这种效应可能达到一个可观测到的量级。在西雅图,牛津,新西伯利亚与莫斯科都已先后分别进行了观测铋蒸汽中宇称不守恒性旋光度的实验,但是迄今为止,测量的结果是不相一致的。旋光角φPNC在扫频时,应当按照与磁偶极吸收线相应的折射率n的色散曲线形式。 The weak interaction theory of Weinberger-Salam suggests that there is a parity-free (PNC) effect in atoms, and this effect may reach an observable magnitude in heavy atoms. In Seattle, Oxford, Novosibirsk and Moscow, experiments have been carried out to observe the parity-free optical rotation in bismuth vapor, respectively, but so far the results of the measurements are not consistent. The rotation angle φPNC should be in the form of a dispersion curve of refractive index n corresponding to the absorption line of the magnetic dipole when swept.