Nuclear moments and isotope shifts of 135La, 137La, and 138La by collinear laser spectroscopy
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The isotope shifts and hyperfine-structure-splitting constants of the 6s21S0-5d6p 3D1 (=538.2 nm) and 5d23P2-5d6p 1D2 (=548.4 nm) transitions of La II have been measured by collinear laser-ion-beam spectroscopy for the accelerator-produced isotopes 135La and 137La, and for the naturally occurring isotopes 138La and 139La. The magnetic moments of the ground states of the isotopes 135La and 137La have been determined to be (135)= +3.70(9)N and (137)=+2.700(15)N, respectively, and the quadrupole moments to be Q(135) =-0.4(4) e b and Q(137)=+0.21(3) e b. The ratio of the magnetic dipole coupling constants A(138)/A(139) of the level 5d6p 3D 1 has shown a -0.35(23)% hyperfine anomaly with respect to the NMR ratio of the nuclear g factors. The change in the mean-square nuclear charge radius determined from the isotope shift between 139La and 135La is r2135,139=0.08(3) fm2. This value is smaller than the predictions made by the finite-range droplet model or by the Hartree-Fock plus BCS calculation.