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Single ion spectroscopy in preparation of an atomic parity violation measurement in Ra+

PhD ceremony:Ms M. Nunez Portela
When:January 09, 2015
Supervisor:prof. dr. K.H.K.J. (Klaus) Jungmann
Co-supervisor:dr. L. Willmann
Where:Academy building RUG
Faculty:Science and Engineering
Single ion spectroscopy in preparation of an atomic parity
violation measurement in Ra+

Precision measurements of Atomic Parity Violation (APV) provide a stringent test for the Standard Model (SM) of particle physics. The determination of the Weinberg angle (sin^2θ_W) at low energies enables in particular a search for physics beyond the SM.

The precision to which this parameter can be obtained depends on the accuracy of the knowledge of the atomic wave functions which can be accurately calculated for systems with one valence electron such as Ba+ and Ra+ ions.   APV effects are much larger in heavy atoms, therefore Ra^+ is  a well suited system for such a measurement. In this work we exploit trapping and laser spectroscopy of different Ra+ isotopes. The frequency for the 7s^2S_(1/2)-6d^2D_(3/2) transition  in the isotopes (212-214)Ra+ has been determined to better than 19MHz.

A competitive APV measurement with Ra+ requires a single localized ion.  Since all Ra+ isotopes are radioactive,  a single ion experiment is developed at the Van Swinderen Institute in the chemical homologue Ba+ as a  precursor to Ra+.  Laser spectroscopy and lifetime measurements have been  performed in a single Ba+ ion. The frequencies of the 6s^2S_(1/2)-6p^2P_(1/2), 5d^2D_(3/2)-6p^2P_(1/2) and 6s^2S_(1/2)-5d^2D_(3/2) transitions have been measured to 3MHz accuracy.

These values are the to date most precise measurements. The lifetime of the 5D_(5/2) state is determined to be τ_(5D_(5/2))=26.4(1.7)s  in good agreement with theoretical predictions and within two standard deviations of  previous measurements. These values provide input for more precise atomic theory calculations in Ba+. The results obtained for Ba+ guide the path towards an  APV measurement in Ra+.

See also the report in the University Newspaper: