title: Hyperfine Anomalies in Fr: Boundaries of the Spherical Single Particle Model.
abstract: We have measured the hyperfine splitting of the 7P_{1/2} state at the 100 ppm level in Fr isotopes (^{206g,206m,207,209,213,221}Fr) near the closed neutron shell (N=126 in ^{213}Fr). The measurements in five isotopes and a nuclear isomeric state of francium, combined with previous determinations of the 7S_{1/2} splittings, reveal the spatial distribution of the nuclear magnetization, i.e., the Bohr-Weisskopf effect. We compare our results with a simple shell model consisting of unpaired single valence nucleons orbiting a spherical nucleus, and find good agreement over a range of neutron-deficient isotopes (^{207-213}Fr). Also, we find near-constant proton anomalies for several even-N isotopes. This identifies a set of Fr isotopes whose nuclear structure can be understood well enough for the extraction of weak interaction parameters from parity nonconservation studies.
authors.affiliation: Department of Physics, Joint Quantum Institute, University of Maryland, and National Institute of Standards and Technology, College Park, Maryland 20742, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: TRIUMF, Vancouver, British Columbia V6T 2A3, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Tandecki
authors.affiliation: Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Collister
authors.affiliation: Department of Physics, College of William and Mary, Williamsburg, Virginia 2319, USA.
authors.forename: S
authors.initials: S
authors.lastname: Aubin
authors.affiliation: TRIUMF, Vancouver, British Columbia V6T 2A3, Canada.
authors.forename: J A
authors.initials: JA
authors.lastname: Behr
authors.affiliation: Instituto de Física, Universidad Autónoma de San Luis Potosí, San Luis Potosí 78290, México.
authors.forename: E
authors.initials: E
authors.lastname: Gomez
authors.affiliation: Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Gwinner
authors.affiliation: Department of Physics, Joint Quantum Institute, University of Maryland, and National Institute of Standards and Technology, College Park, Maryland 20742, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Orozco
authors.affiliation: TRIUMF, Vancouver, British Columbia V6T 2A3, Canada.
authors.forename: M R
authors.initials: MR
authors.lastname: Pearson
authors.affiliation: Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Sprouse