Testing time-reversal symmetry usingHg199

A new search for a permanent electric dipole moment of ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ has yielded the null result d${(}^{199}$Hg)=-(2.7±5.8)×${10}^{\mathrm{-}28}$e cm where the statistical and systematic uncertainty have been combined. This gives an upper limit of d${(}^{199}$Hg)<1.3×${10}^{\mathrm{-}27}$e cm (95% confidence). The measurement sets the most stringent limits to date on several possible sources of time-reversal symmetry violation. We look for a relative shift in Larmor-precession frequency between two optically pumped ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ atomic oscillators in the presence of applied electric fields. We have attained a statistical uncertainty on the relative shift in frequency between the oscillators of 2×${10}^{\mathrm{-}9}$ Hz.