Hyperfine Anomaly Measurements in Francium Isotopes and the Radial Distribution of Neutrons

J. S. Grossman, L. A. Orozco, M. R. Pearson, J. E. Simsarian,* G. D. Sprouse, and W. Z. Zhao Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3800 (Received 5 April 1999) We have measured the hyperfine structure of the 7P1 2 level for 2082212Fr to a precision of 300 ppm. These measurements along with previous ground state hyperfine structure measurements reveal a hyperfine anomaly. The hyperfine anomaly exhibits a strong sensitivity to the radial distribution of the neutron magnetization, providing a good way to probe this quantity. We use neutron radial distributions from recent theories to qualitatively explain the measurements.