Laser Cooling of Radium Ions

Area of Science:

• Atomic physics
• Nuclear physics
• Quantum information science

Background:

• Unstable radium nuclei are valuable for new physics research due to their mass, octupole deformation, and energy levels.
• Ion traps are ideal for radioactive species like radium ions, enabling experiments with low particle numbers and long hold times.
• Challenges exist in studying radium due to the lack of stable isotopes.

Purpose of the Study:

• To overcome challenges in studying unstable radium isotopes.
• To perform laser cooling of trapped radium ions using a low-activity source.
• To measure fundamental properties of the radium atom for precision measurements.

Main Methods:

• Utilized a low-activity (∼10 μCi) radium source in a tabletop experiment.
• Employed laser cooling techniques to trap and cool radium ions.
• Measured branching fractions of the 7p^{2}P_{1/2}^{o} state and the 7s^{2}S_{1/2}→7p^{2}P_{1/2}^{o} transition frequency using a tellurium reference line.

Main Results:

• Successfully laser-cooled trapped radium ions from a low-activity source.
• Measured the branching fractions of the 7p^{2}P_{1/2}^{o} state to the ground state (7s^{2}S_{1/2}) as 0.9104(7) and to the metastable 6d^{2}D_{3/2} state as 0.0896(7).
• Determined the 7s^{2}S_{1/2}→7p^{2}P_{1/2}^{o} transition frequency to be 640.09663(6) THz.

Conclusions:

• Demonstrated the feasibility of laser-cooling low-activity radium ions for precision measurements.
• Provided crucial atomic data for radium, enabling its use in fundamental physics research.
• Opened avenues for exploring new physics with unstable radium isotopes using accessible experimental setups.