Nuclear Moments of the Neutron-Deficient Lanthanum Isotopes by Collinear Laser Spectroscopy

The hyperfine-structure-splitting constants and isotope shifts of the 6s$^{2}$ $^{1}$S$_{0}$-5d6p $^{3}$D$_{1}$ ($\lambda$=538 nm) and 5d$^{2}$ $^{3}$P$_{2}$-5d6p $^{1}$D$_{2}$ ($\lambda$=548 nm) transitions of singly charged lanthanum ion have been measured by collinear laser-ion-beam spectroscopy for the neutron-deficient isotopes $^{135}$La, $^{137}$La, and $^{138}$La. The magnetic moments and quadrupole moments of the ground states of these isotopes have been determined from the measurements. The ratio of the magnetic dipole coupling constants A(138)/A(139) of the level 5d6p $^{3}$D$_{1}$ has shown a -0.35(23)$\%$ hyperfine anomaly with respect to the NMR ratio of the nuclear g factors. These moments and the changes in the mean-square nuclear charge radii determined from the isotope shifts are compared with theoretical predictions. Work to measure more neutron-deficient lanthanum isotopes is in progress by our laser spectroscopy collaboration at the ISAC facility at TRIUMF.