High precision measurement of the D-line tune-out wavelength in 87Rb using a Bose-Einstein condensate interferometer

An atom-wave interferometer using a Bose-Einstein condensate of 87Rb in the F = 2 hyperfine ground state was used to measure the wavelength of light at which the scalar dynamic electric polarizability equals zero. Vector contributions to the polarizability are minimized through the use of linearly polarized light. The polarization of the light is measured at the atoms using the same atom-wave interferometer. A rotating magnetic field further reduces the vector polarizability through temporal averaging. Tensor contributions to the polarizability are measured, and removed from the value reported here. The wavelength is measured using a wavemeter which was calibrated using known saturation absorption lines in K, Rb, and Cs. The tune-out wavelength between the 5S ground state and 5P excited states was found to be 790.032326(32) nm. This measurement marks a 50-fold improvement over previous tune-out wavelength measurements. The measured tune-out wavelength is used to determine the ratio of matrix elements d_5P3/2 / d_5P1/2 = 1.99217(3), a 100-fold improvement over previous experimental values. A theoretical determination of the tune-out wavelength is found to be consistent with the experiment, with uncertainty estimates for the theory about an order of magnitude larger than the experimental precision.