SEMINAR: Physics Seminar

The Observatoire de Paris has a long history of time keeping and today is one of the leading contributors to Coordinated Universal Time. A new clock on-the-block is that based on neutral mercury atoms. It is one of a new genre of atomic clocks that confines the neutral atoms in the Lamb-Dicke regime, where the motion of atoms is constrained to within half the wavelength of the interacting light — thereby avoiding Doppler and recoil shifts. To confine atoms in such a trap, the atoms are cooled, typically in a magneto-optical trap, before being transferred to a lattice of light-shift induced potential wells. Once trapped, the atoms interact with a probe signal (254nm) that excites the doubly forbidden 1S0- 3P0 transition (permitted for fermionic and "quenched" bosonic isotopes). Such experiments have been performed for strontium and ytterbium. Mercury is the next of the divalent atoms to be explored and warrants investigation because it is ~20 times less sensitive to blackbody radiation (a dominant contributor to the uncertainty in Sr and Yb clocks). However, there are obstacles: producing adequate quantities of deep UV light for the cooling and probing of the atoms, and producing sufficiently deep potential wells at the so-called magic-wavelength. Despite this the group has made some exciting advances in the Hg clock's development, which will be reviewed during this seminar.