Inner-shell magnetic dipole transition in Tm atom as a candidate for optical lattice clocks

TL;DR

This paper proposes using a narrow magneto-dipole transition in Tm atoms at 1.14 μm for optical lattice clocks, demonstrating low BBR sensitivity and potential for high precision with estimated uncertainties below 5×10⁻¹⁸.

Contribution

It identifies a specific Tm transition as a promising candidate for optical lattice clocks and calculates key properties including the magic wavelength and perturbation effects.

Findings

Magic wavelength at 807 nm for the optical lattice.

BBR shift sensitivity estimated at 8×10⁻¹⁷ fractional units.

Upper clock level lifetime exceeds 112 ms, linewidth narrower than 1.4 Hz.

Abstract

We consider a narrow magneto-dipole transition in the $^{169}$Tm atom at the wavelength of $1.14\,\mu$m as a candidate for a 2D optical lattice clock. Calculating dynamic polarizabilities of the two clock levels $[\text{Xe}]4f^{13}6s^2 (J=7/2)$ and $[\text{Xe}]4f^{13}6s^2 (J=5/2)$ in the spectral range from $250\,$nm to $1200\,$nm, we suggest the "magic" wavelength for the optical lattice at $807\,$nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction and other effects which can perturb the transition frequency are calculated. The transition at $1.14\,\mu$m demonstrates low sensitivity to the BBR shift corresponding to $8\times10^{-17}$ in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than $5 \times 10^{-18}$ in fractional units. By direct excitation of the $1.14\,\mu$m transition in Tm atoms loaded into an optical dipole trap, we set the lower limit for the lifetime of the upper clock level $[\text{Xe}]4f^{13}6s^2 (J=5/2)$ of $112\,$ms which corresponds to a natural spectral linewidth narrower than $1.4\,$Hz. The polarizability of the Tm ground state was measured by the excitation of parametric resonances in the optical dipole trap at $532\,$nm.