Nuclear and Electronicg-Factors of²¹¹Fr, Nuclear Ground-State Spin of²⁰⁷Fr and the Nuclear Single-Particle Structure in the Range^207-228Fr

Abstract

The nuclear and electronic magnetic dipole moments of 21Fr and the nuclear ground-state spin of 207Fr have been measured directly by on-line atomic-beam magnetic resonance techniques at the ISOLDE facility at CERN. The following results have been obtained: μI(211Fr) = 4.00(8) nm, gJ(Fr, 7s 2S1/2) = 2.00497(9) and I(207Fr) = 9/2. A large deviation of the electronic magnetic moment from the free electron value was found. Using the measured nuclear magnetic moment μI(211Fr), a comparison is made between different theoretical calculations of the magnetic dipole hyperfine constants and with the available experimental data in 211Fr. An analysis of the electric quadrupole interaction is also given. Nuclear magnetic dipole and electric quadrupole moments are deduced for the sequences 207-213Fr and 220-228Fr, using the data on 211Fr as reference values. The nuclear quantities are discussed within the framework of the shell model and the core-quasiparticle model, giving information on the nuclear single-particle structure and on the variation in deformation along the sequences of francium isotopes.

Nuclear moments and charge radii of neutron-deficient francium isotopes and isomers

“…The odd-even staggering as observed in 207−213 Fr [12] continues to lower masses with a more pronounced effect compared to nuclei in the vicinity of the N = 126 shell closure. For the nuclear ground states, a deviation from the β 2 = 0 line of zero quadrupole deformation is observed at N 119 indicating the loss of a perfectly spherical system.…”

“…5. A single valence proton located in the π 1h 9/2 shell determines the structure of the odd-A, neutron-deficient Fr isotopes [12] giving rise to the I = 9/2 nuclear ground state spins. Such a valence proton couples with a valence neutron in the even-A Fr isotopes to form ground state configurations where the neutron orbital occupancy may be taken directly from the shell model.…”

“…Typically, the neutron-deficient francium nuclei, having five protons in excess to Pb, are considered to consist of an inert * anvoss@jyu.fi Pb core with valence nucleons around it [12]. As the neutron shells are depleted from N = 126 ( 213 Fr) downward, several isotopes have been found to have isomeric states around the N = 118 subshell closure [13].…”

Decay-Assisted Laser Spectroscopy of Neutron-Deficient Francium

“…13. The data of francium show the charge radii of [207][208][209][210][211][212][213] Fr reevaluated by Dzuba et al [46] alongside the CRIS values, which extends the data set to 202 Fr. The blue data points show the francium ground states, while the (7 þ ) isomeric states are in green and the (10 − ) states in red.…”

“…g emp ðπ1h 9=2 Þ is determined from the magnetic moment of the single-particle state in 209 Bi [61]. Similarly, g emp ðπ3s 1=2 Þ is estimated from the magnetic moment of the single-hole ground state in 207 Tl [62]. From N ¼ 126 to 116, every isotope has a g factor consistent with the proton occupying the π1h 9=2 orbital.…”