Can imperfect light polarization mimic parity violation in Stark experiments on forbidden Ml transitions ?

Abstract

Oddness under reversal of the circular polarization of the exciting light is one important criterion to discriminate the parity violation signal. Imperfections of the polarization flipper or anisotropy in the optical components can generate systematic effects by spoiling the polarization and causing even signals to look partly odd. We discuss the interest of reflecting the beam back through the vapour. We indicate various methods to minimize systematic errors and to control their residual magnitude during the parity violation experiment while using the atoms themselves as a probe