The 6¹S₀-6³P₀ transition in thallium isotope ion ²⁰⁴Tl⁺: A superior atomic clock

Abstract

Experimental and theoretical studies of the forbidden J = 0 → J′ = 0 optical transition 6¹ S ₀-6³ P ₀ in the odd Hg isotopes are in the literature. From this work natural width and quadratic Zeeman effect have been estimated for the same line in the isoelectronic, even thallium ion ²⁰⁴Tl⁺, which has a very small nuclear magnetic moment. For the m _F = 0 → 0 component a linewidth of <0.01 Hz and a quadratic Zeeman shift <10^-18 at 0.1 Gauss are found, compared to 1 Hz and ≈10^-8 for the hydrogen maser. Electronic quadrupole moments vanish for both J and J′ states and with them shifts due to electric field gradients. All shifts are orders of magnitude smaller than for Hg⁺ and Ba⁺, which have been studied as atomic clock elements.

• individual ion
• trapped in vacuum
• zero electronic angular momenta
• no frequency shifts