Accurate calculations of Sr properties for a high-accuracy optical clock

TL;DR

This paper presents precise calculations of strontium atomic properties crucial for enhancing the accuracy of optical atomic clocks, aiming to reduce uncertainties below 10^{-17} by improving polarizability measurements.

Contribution

The study provides highly accurate calculations of Sr atomic polarizabilities and identifies key states influencing clock precision, enabling targeted experimental improvements.

Findings

Calculated polarizabilities of Sr clock states with high accuracy

Identified four low-lying states contributing 90% to polarizability

Achieved potential blackbody shift uncertainty below 10^{-17}

Abstract

We have carried out calculations towards the goal of reducing the inaccuracy of the Sr optical atomic clock to 1$\times10^{-17}$ and below. We calculated a.c. polarizabilities of the $5s^2 ^1S_0$ and $5s5p ^3P_0^o$ clock states that are important for reducing the uncertainty of blackbody radiation-induced frequency shifts for the $^1S_0 - ^3P_0^o$ clock transition. We determined four low-lying even-parity states whose total contribution to the static polarizability of the $^3P_0^o$ clock state is at the level of 90%. We show that if the contribution of these states is experimentally known with 0.1% accuracy, the same accuracy can be achieved for the total polarizability of the $^3P_0^o$ state. The corresponding uncertainty for the blackbody shift at a fixed room temperature will be below 1$\times10^{-17}$. The calculations are confirmed by a number of experimental measurements on various Sr properties.