Search for EDM in atoms, molecules and the neutron. CP and T Violation in atomic physics.
Hg Electric Dipole (EDM)

Experimental Setup
Hg Cells
Probing Atomic Precession EDM Experiments

(Click on regions of setup for more detail)

UV laser system at 254 nm: Hg 1S0 3P1 line.

  • Solid state system for long term stability and low noise.

  • Start with SDL MOPA (Master Oscillator, Power Amplifier):0.5 W at 1016 nm.

  • First doubling cavity uses KNbO3 crystal, type I phase-matching.

  • Obtain 130 mW at 507 nm.

  • Astigmatism due to walk-off compensated by cylindrical leanses.

  • Second cavity uses Brewter-cut BaB2O4 (BBO) crystal.

  • Obtain 6 mW at 254 nm using superpolished mirrors in the second cavity.

  • Amplitude noise 10^-4 nms/Hz^1/2.


The laser allows us to scan across the Hg absorption lines.

Hg Cells

We use paraffin coating to reduce surface spin relaxation of 199Hg

Several other types of coatings were tested, including: Surfasil, Aquasil, Drifilm, but paraffin worked the best.
Magnetic field dependence of the relaxation rate:

Probing Atomic Precession

We use pump and probe method, alternating between optical pumping and probing atomic precession. For optical pumping we chop circularly polarized laser light at the Larmor frequncy of the spins, pumping them into a rotating frame. For probing the precession we use linearly polarized light and detect the rotation of the plane of the polarization produced by the spins.

Optical Rotation Signal

Mike Romalis and Siobhan Quinn
August 1999