Atomic parity violation in a single trapped radium ion

摘要

Atomic parity violation (APV) experiments are sensitive probes of the electroweak interaction at low energy. These experiments are competitive with and complementary to high-energy collider experiments. The APV signal is strongly enhanced in heavy atoms, and it is measurable by exciting suppressed (M1, E2) transitions. The predicted enhancement factor of the APV effect in the S-D transition in Ra+ is about 50 times larger than the S-S transition in neutral Cs. However, certain spectroscopic information on Ra ~+, needed to constrain the required atomic many-body theory, was lacking. Using the AGOR cyclotron and the TRIμP facility at KVI in Groningen, short-lived ~(212-214)Ra~+ ions were produced and trapped. First ever excited-state laser spectroscopy was performed on the trapped ions. These measurements provide a benchmark for the atomic theory required to extract the electroweak mixing angle to sub 1% accuracy and are an important step towards an APV experiment in a single trapped Ra~+ ion. A lower bound on the radiative lifetime of the 6~2D_(5/2) state was found of 232(4) ms. This experimental confirmation of the long coherence time of the meta-stable 6~2D_ (5/2) state is important in light of the possibility of using a single trapped radium ion as an optical frequency standard.