Some Rare Earth Spins, and the Hyperfine Structure of¹⁷⁶Lu

The nuclear spins of the isotopes 143 Nd, 145 Nd, 147 Sm, 149 Sm, 161 Dy, 163 Dy, 167 Er and 176 Lu have been measured by the atomic-beam magnetic-resonance technique. Earlier paramagnetic resonance results for the first seven isotopes have been confirmed, and we have shown that the spin I of 176 Lu is definitely 7. The shell model accounts for the ground-state spins of the first four isotopes, and the collective model for those of the Dy, Er and Lu isotopes. The hyperfine structure of 176 Lu in the state 2 D 3/2 has been determined from Δ F = O resonances and the following values of the dipole A and quadrupole B interaction constants give a good fit to the experimental data: A = (+)138.8 ± 1.0 Mc/s, B = (+)2151 ± 20 Mc/s. Unpublished measurements by Ritter of 175 gI , A ( 2 D 3/2 ) and A ( 2 D 5/2 ) for 175 Lu were used to estimate the magnitude of an s-electron configuration admixture to A ( 2 D 3/2 ) in 176 Lu, and the following values of the 176 Lu nuclear moments were then deduced: 176 μ = (+)3.07 ± 0.28 nm, 176 Q = (+)8.0 ± 0.7 bn. The collective model with strong surface coupling predicts that 175 Q / 176 Q = 0.697 compared with the experimental ratio 175 B / 176 B = 0.702 (8), which is obtained by combining our results with those of Ritter.