Comparison of hyperfine anomalies in the 5S_{1/2} and 6S_{1/2} levels of   ^{85}Rb and ^{87}Rb
  We observe a hyperfine anomaly in the measurement of the hyperfine splitting of the 6S_{1/2} excited level in rubidium. We perform two step spectroscopy using the 5S_{1/2}->5P_{1/2}->6S_{1/2} excitation sequence. We measure the splitting of the 6S1/2 level and obtain for the magnetic dipole constants of ^{85}Rb and ^{87}Rb A = 239.18(4) MHz and A=807.66(8) MHz, respectively. The hyperfine anomaly difference of_{87}delta_{85}=-0.0036(2) comes from the Bohr Weisskopf effect: a correction to the point interaction between the finite nuclear magnetization and the electrons, and agrees with that obtained in the 5S_{1/2} ground state. 
A. Perez Galvan (1), Y. Zhao (1), L. A. Orozco (1), E. Gomez (2), A.   D. Lange (2), F. Baumer (2), G. D. Sprouse (2) ((1)De...