# Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

Abstract : The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\delta\langle r^{2}\rangle^{A,221}$ values for $^{218m,219}\text{Fr}$ and $^{229,231}\text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\text{Fr}$ has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The $g(^{219}\text{Fr}) = +0.69(1)$ value supports a $\pi 1h_{9/2}$ shell model configuration for the ground state. The $g(^{229,231}\text{Fr})$ values support the tentative $I^{\pi}(^{229,231}\text{Fr}) = (1/2^{+})$ spin, and point to a $\pi s_{1/2}^{-1}$ intruder ground state configuration.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-01065500
Contributor : Sophie Heurteau <>
Submitted on : Thursday, September 18, 2014 - 10:56:37 AM
Last modification on : Wednesday, September 16, 2020 - 4:08:37 PM

### Citation

I. Budinčević, J. Billowes, M. L. Bissell, T. E. Cocolios, R. P. de Groote, et al.. Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry. Physical Review C, American Physical Society, 2014, 90, pp.014317. ⟨10.1103/PhysRevC.90.014317⟩. ⟨in2p3-01065500⟩

Record views