Anapole moment Measurements in Atomic Cesium
6S Ground state hyperfine transition
Transition diagram for the 6S hyperfine ground state measurement setup (diagram is not drawn to scale)
The PNC amplitude can be measured from the excitation of the 6S ground hyperfine transition. As shown in the diagram, 6S → 6S transition is excited by Raman lasers and a microwave field at 9.2 GHz. This transition has a very narrow band and commonly known as the atomic clock transition. The main contributions to the excitation of this transition are a two-photon Raman pathway, the Stark-induced transition, and the PNC transition. The magnetic dipole transition is usually large for microwave transitions but in this setup the magnetic dipole moment is severely suppressed by the microwave cavity resonator.
Figure (a) Experimental setup for the PNC measurement in cesium ground hyperfine states (b) Microwave cavity resonator for excitation of the PNC transition in the cesium ground hyperfine states.
The lasers and the microwave field are all phase-locked. This is to observe interference among different transition amplitudes while changing the relative phases. The high finesse cavity is devised such that the microwave field is highly pure and can build up power in the interaction region significantly. A similar experimental setup has been devised at TRIUMF where researchers are trying to create and trap Francium atoms in a MOT and measure the PNC amplitude. For more information, please access our ArXiv paper or more up-to-date PRA publication.