Collinear laser spectroscopy on neutron-rich actinium isotopes

High-resolution collinear laser spectroscopy of neutron-rich actinium has been performed at TRIUMF’s isotope separator and accelerator facility ISAC. By probing the $7s^2{}^1{S}_0$ $\to$ $6d7p{}^1{P}_1$ ionic transition, the hyperfine structures and optical isotope shifts in ${}^{225,226,228,229}\text{\hspace{0.17em}⁣}$Ac${}^{+}$ have been measured. This allows precise determinations of the changes in mean-square charge radii, magnetic dipole moments, and electric quadrupole moments of these actinium isotopes. The improved precision of charge radii and magnetic moments clears the ambiguity in the odd-even staggering from previous studies. The electric quadrupole moments of ${}^{225,226,228,229}\text{\hspace{0.17em}⁣}$Ac are determined for the first time.