Accurate calculations of Sr properties for a high-accuracy optical clock
Abstract
We have carried out calculations towards the goal of reducing the inaccuracy of the Sr optical atomic clock to 1×10-17 and below. We calculated a.c. polarizabilities of the 5s2 1S0 and 5s5p 3P0o clock states that are important for reducing the uncertainty of blackbody radiation-induced frequency shifts for the 1S0 - 3P0o clock transition. We determined four low-lying even-parity states whose total contribution to the static polarizability of the 3P0o 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 3P0o state. The corresponding uncertainty for the blackbody shift at a fixed room temperature will be below 1×10-17. The calculations are confirmed by a number of experimental measurements on various Sr properties.