Atomic parity violation measurements in the highly forbidden 6S 1/2-7S1/2 caesium transition. - I. Theoretical analysis, procedure and apparatus

Abstract

This paper is the first part of a detailed presentation of parity violation measurements performed in two hfs components of the highly forbidden 6S-7S transition of the Cs atom. Under excitation by a circularly polarized laser in a dc electric field, interference takes place between an electromagnetic amplitude induced by the field and the parity-violating amplitude induced by weak interactions. This interference gives rise in the electronic polarization of the 7S state to a contribution which behaves like a vector when the handedness of the experiment is reversed In principle, only this contribution is observed in the chosen direction of observation. Detection proceeds through the circular polarization ratio of the 7S-6P1/2 fluorescence. By Hanle effect in a magnetic field applied periodically, the parity-conserving contribution is observed in the same way and used to calibrate the experiment. The final result is the ratio Im Epv1/β of the parity-violating amplitude to the vector polarizability. Our value is ( — 1.56 ± 0.17 (stat.) ± 0.12 (syst.)) mV/cm. In what follows, we give the formulae for all available atomic signals and describe the apparatus and procedures