Parity non-conserving Measurements in Atomic Cesium
The weak charge can be derived from the transition amplitudes of the highly forbidden transition, 6S → 7S, where the transition becomes weakly allowed due to the weak interaction between the nucleons and the valence electron. The transition amplitude is many orders magnitude smaller than a regular electric-dipole-allowed transition, which makes it extremely susceptible to noise and other systematic errors. Although the most recent measurement results of the transition have appreciably low uncertainty, a better measurement will not only shed light on the nature of the weak force but also provide a unique probe for the search of dark matter.
Anapole moment Measurements in Atomic Cesium
An anapole moment of the nucleus arises from the weak nucleon-nucleon interaction due to neutral current in the nucleus. Only one measurement of an anapole moment has been successful so far; a measurement from the Boulder group nearly two decades ago. That moment was much larger than expected, and is not in agreement with other models of nuclear interactions. While the Boulder group derived the anapole moment by comparing two optical PNC transitions, namely 6S1/2 F=3 → 7S1/2 F=4 and 6S1/2 F=4 → 7S1/2 F=3, our approach is the direct excitation of the ground state hyperfine PNC transition 6S1/2 F=3 → 6S1/2 F=4 with microwave fields and Raman lasers.
In support of the PNC measurements described above, we have undertaken a series of precision measurements of electric dipole transition matrix elements in atomic cesium. These include measurements of (1) the absorption coefficient of the 6s → 7p transition, (2) the lifetime of the 7s state, (3) the relative strengths of the 7s→ 6p2P1/2 and 7s→ 6p 2P3/2 transitions using a two-color, two-photon excitation scheme to; and (4) the lifetime of the 7p states.