High-precision measurements of the 87Rb D-line tune-out wavelength

We report an experimental measurement of a light wavelength at which the ac electric polarizability equals zero for Rb-87 atoms in the F = 2 ground hyperfine state. The experiment uses a condensate interferometer both to find this tune-out wavelength and to accurately determine the light polarization for it. The wavelength lies between the D1 and D2 spectral lines at 790.032388(32) nm. The measurement is sensitive to the tensor contribution to the polarizability, which has been removed so that the reported value is the zero of the scalar polarizability. The precision is 50 times better than previous tune-out wavelength measurements. Our result can be used to determine the ratio of matrix elements vertical bar < 5P(3/2)parallel to d parallel to 5S(1/2)>/< 5P(1/2)parallel to d parallel to 5S(1/2)>vertical bar(2) = 1.99221(3), a 100-fold improvement over previous experimental values. New theoretical calculations for the tune-out wavelength and matrix element ratio are presented. The results are consistent with the experiment, with uncertainty estimates for the theory about an order of magnitude larger than the experimental precision.