We are investigating the possibilities of using neutral mercury as a new species to realize a highly accurate atomic clock using the non-perturbing dipole lattice trapping scheme. Typically, accuracy below 10-17 is targeted, which would make neutral mercury an interesting candidate for a redefinition of the SI second. This paper presents our on-going work towards the realization of an optical lattice clock using neutral mercury. We will describe a 254 nm laser source delivering several hundreds of milliWatts at this wavelength with a suitably low frequency noise for laser cooling and magneto-optic trapping. We will describe our vacuum system for magneto-optic trap and report on the status of our work regarding magneto-optic trapping of mercury. We will also describe our clock laser at 266 nm.
We report on a frequency ratio measurement of a
199Hg-based optical lattice clock referencing a
87Sr-based clock. Evaluations of lattice light shift, including atomic-motion-dependent shift, enable us to achieve a total systematic uncertainty of $7.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ for the Hg clock. The frequency ratio is measured to be ${\ensuremath{\nu}}_{\mathrm{Hg}}/{\ensuremath{\nu}}_{\mathrm{Sr}}=2.629\text{ }314\text{ }209\text{ }898\text{ }909\text{ }60(22)$ with a fractional uncertainty of $8.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$, which is smaller than the uncertainty of the realization of the International System of Units (SI) second, i.e., the SI limit.
Optical lattice clocks combine the accuracy and stability required for next-generation frequency standards. At the heart of these clocks are carefully engineered optical lattices tuned to a wavelength where the differential AC Stark shift between ground and excited states vanishes—the so called ‘magic’ wavelength. To date, only alkaline-earth-like atoms utilizing clock transitions with total electronic angular momentum J=0 have successfully realized these magic wavelength optical lattices at the level necessary for state-of-the-art clock operation. In this article, we discuss two additional types of clock transitions utilizing states with J≠0, leveraging hyperfine structure to satisfy the necessary requirements for controlling lattice-induced light shifts. We propose realizing (i) clock transitions between same-parity clock states with total angular momentum F=0 and (ii) M1/E2 clock transitions between a state with F=0 and a second state with J=1/2, mF=0. We present atomic species which fulfill these requirements before giving a detailed discussion of both manganese and copper, demonstrating how these transitions provide the necessary suppression of fine structure-induced vector and tensor lattice light shifts for clock operations. Such realization of alternative optical lattice clocks promises to provide a rich variety of new atomic species for neutral atom clock operation, with applications from many-body physics to searches for new physics.