Determination of Sr properties for a high-accuracy optical clock

We have carried out calculations towards the goal of reducing the inaccuracy of the Sr optical atomic clock to 1 x 10(-17) and below. In particular, we focused on ac polarizabilities of the 5s(2) S-1(0) and 5s5p 3P(0)(o) clock states that are important for reducing the uncertainty of black-body radiation-induced frequency shifts for the S-1(0)-P-3(0)o clock transition. Four low-lying even-parity states have been identified, whose total contribution to the static polarizability of the P-3(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 P-3(0)o state. The corresponding uncertainty for the blackbody shift at a fixed room temperature will be below 1 x 10(-17). The calculations are confirmed by a number of experimental measurements on various Sr properties.