Measurement of the D-line Vector Polarizability in 87Rb Using Tune-out Wavelength Spectroscopy

A Bose-condensate atom interferometer is used to measure vector tune-out wavelengths in 87Rb. These are the polarization dependent wavelengths at which the ac electric polarizability equals zero. Precision control of the rotating magnetic bias field is demonstrated. This field is then used to vary the optical polarization in a controlled manner at the 10^−5 level. This shifts the tune-out wavelength and the measured polarization dependence of the tune-out wavelengths is used to determine the various contributions to the polarizability including that of the core electrons, and notably the higher-lying dipole matrix element “tail” components. These tails are of importance to the theoretical analysis of atomic parity violation and other fundamental physics measurements. We report the first experimental measurement of tail components of the electric polarizability. These are |t1/2|^2 = 5(4) au and |t3/2|^2 = −4(4) au for the n′J1/2 and n′J3/2 components respectively. Within the experimental uncertainty they are in agreement with the best current estimates of these contributions |t1/2|^2 = 0.022(22) au and |t3/2|^2 = 0.075(75) au. Improvements to the experimental design to improve the experimental precision and place a better constraint on the tail values are discussed.