Progress towards an Improved Measurement of the Radium-225 Electric Dipole Moment

Experimental observation of a permanent electric dipole moment (EDM) in a non-degenerate system would provide direct evidence for beyond-Standard Model symmetry violation that is necessary to explain the observed matter—anti-matter asymmetry of the Universe. ²²⁵Ra (t_1/2=15 d, I=1/2) is a particularly attractive system to test for an EDM because its octupole-deformed nucleus, closely spaced nuclear ground-state parity doublet, and highly relativistic electrons enhance the observable atomic EDM resulting from fundamental symmetry violation in the nuclear medium. Previous measurements have limited the EDM of ²²⁵Ra to less than 1.4 × 10^-23 e cm (95% CL). We report progress toward implementing experimental upgrades that will enable measurements at the 10^-26 e cm level. In particular, we describe advances in laser cooling and trapping radium using a strong, dipole allowed ¹S₀ to ¹P₁ electronic transition at 483 nm. Compared to previous techniques, 483 nm laser cooling and trapping will greatly enhance EDM measurement precision by increasing the number of atoms participating in the measurement.