Measurement of the differential polarizability of the 698 nm clock transition of strontium for evaluation of optical lattice clocks

A modification to a successfull technique to measure static differential polarizabilities of ultracold atoms and molecules is presented. Ultracold atoms are trapped in a magic wavelength optical lattice and transported into the field of a precision capacitor. The change of the transition frequency induced by the applied field, which is controlled to better than 10^-4, is measured. For atomic clocks, the difference of the static polarizabilies of ground and excited state is closely related to their response to a blackbody radiation field, which is a significant contribution to the uncertainty budget of many atomic clocks.